FERRIC  and 

HELIOGRAPHIC 
PROCESSES 


George  E.  Brown   F.I.C. 


FERRIC  AND   HELIOGRAPHIC 
PROCESSES. 


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R  handbook  for  PbotoarapDers, 
Drausbtsmen,  ana  Sun  Printers 


By  GEORGE  E.  BROWN,  FJ.G 

{Late  of  the  G.    W.  Railway  Co.   Chemical  Staff ; 
Joint- Editor  of  "  The  Photogram") 


Second  Edition 


TENNANT  &  WARD 

287    FOURTH    AVENUE 

NEW    YORK 


h 


INTRODUCTION 


This  little  handbook  is  intended  to  serve  two  classes 
of  people.  First,  amateur  photographers,  with  a 
taste  for  experiment,  who  may  find  in  the  prepara- 
tion of  their  own  sensitive  papers  much  interesting 
work ;  and,  secondly,  draughtsmen,  engineers, 
architects,  surveyors,  and  others,  who  find  the 
reproduction  of  tracings  and  drawings  a  matter  of 
every-day  necessity. 

It  would  have  been  easy  to  have  made  the  manual 
greatly  exceed  its  present  proportions  ;  but  the  writer 
has  preferred  to  omit  any  notice  of  those  processes, 
the  difficulty  or  unreliability  of  which  only  makes 
their  employment  disappointing.  Much,  too,  that 
might  have  been  said  on  theoretical  matters  is 
omitted,  the  aim  of  the  book  being  to  be  strictly 
practical. 

Mr  W.  E.  Brewerton  has  kindly  supplied  particu- 
lars of  the  process  described  in  Chapter  IV. 


PREFACE  TO  SECOND  EDITION. 


Revisions  and  additions  have  been  made  as  called 
for  by  the  expansion  of  the  subject.  The  writer 
believes  that  the  volume  as  it  now  stands  represents 
our  current  knowledge  of  these  iron  printing  processes 
and  their  technical  uses. 


CONTENTS 


IHAP.  PAGE 

I.   THE   FERRO-PRUSSIATE   PROCESS,             .           .           .  11 

II.   TONING  BLUE   PRINTS, 17 

III.   THE   USES   OP   BLUE   PRINTS,           ....  23 

IV.    FERRO-PRUSSIATE   IN   TRI-COLOR   WORK,        .           .  29 

V.   THE   KALLITYPE   PROCESS,      .           .           .    '                   .  32 

VI.    THE   OBERNETTER   PROCESS,             ....  45 

VII.   THE   URANOTYPE    PROCESS, 49 

VIII.    PRINTS   ON   FABRICS — PRINTS   IN   DYES,          .           .  53 

IX.    HELIOGRAPHIC   PROCESSES   COMPARED,            .           .  56 

X.   PREPARATION   OF   HELIOGRAPHIC   PAPERS,    .           .  59 

XI.   MAKING  TRACINGS   FOR   SUN-COPYING,             .           .  75 

XII.   OUTFIT   FOR   HELIOGRAPHIC   PRINTING,           .           .  77 

XIII.  FERRO-PRUSSIATE,  OR  WHITE  LINE  ON  BLUE  GROUND,   90 

XIV.  PELLET,   OR   BLUE   LINE   ON  WHITE   GROUND,         .  94 
XV.   FERRO-GALLIC,  OR  BLACK  LINE  ON  WHITE  GROUND,  99 

XVI.   BROWN  LINE   ON   WHITE   GROUND,  .  .  .102 

XVII.    MINOR   HELIOGRAPHIC   PROCESSES,         .           .           .  105 


10 


CONTENTS 


CHAP. 

XVIII.    PRINTING    HOUSE   MEMORANDA, 

XIX.    MANIPULATION,     . 

XX.    PAPER   AND   SIZING, 

XXI.    CHEMICALS, 

XXII.    CHEMISTRY, 

BIBLIOGRAPHY,      . 

INDEX, 


PAGE 

115 
117 
126 
132 
139 
146 
148 


FERRIC    AND    HELIOGMPHIC 

PROCESSES 


CHAPTEB     I 

The  Ferro-Prussiate  Process 

Theory  in  Brief. — -Paper  is  coated  with  a  mixture 
of  ferric  salt  and  potassium  ferricyanide :  ou 
exposure  to  light,  the  ferric  salt  is  reduced  to 
ferrous  salt,  which  gives,  with  the  ferricyanide, 
a  precipitate  of  TurnbulFs  blue. 

The  ferro-prussiate  can  claim  to  be  one  of  the 
oldest  printing  processes,  for  it  was  used  by  Herschel, 
in  substantially  its  present  form,  in  1840.  Tor 
simplicity  and  permanency  it  is  second  to  none. 
The  color  of  its  image  is  not  one  which  fits  the 
process  for  regular  and  systematic  use  ;  but  many 
subjects,  particularly  seascapes  and  cloudscapes. 
river  and  lake  scenery,  and  others,  into  the  composi- 
tion of  which  water  enters,  are  admirably  suited  for 
reproduction  by  the  blue  process.  The  color  of  the 
blue  linage  can  be  altered  in  various  wavs,  though 

not  alwavs  with  the  most  satisfactory  results. 

11 


12  FERRIC   AND   itELtOGRAPHlC    PROCESSES 

The  paper  for  blue  printing  is  best  sensitised  at 
home  rather  than  bought  ready-made.  The  amateur 
may  not  be  able  to  make  a  paper  that  will  keep  a 
long  time,  but  he  will  have  no  difficulty  at  all  in 
preparing  one  that  will  give  far  better  results  than 
much  of  the  paper  obtained  in  commerce. 

Here,  then,  is  a  simple  and  easily-worked  formula. 
Make  two  solutions  : — 

(1)  Ferric  am.  citrate  (red),     80  grains.       183  grams. 
Water,  ...       1  ounce.      1000  c.cs. 

(2)  Potass  ferricyanide,       .     60  grains.       137  grams. 
Water,  ...       1  ounce.      1000  c.cs. 

Unless  the  ferricyanide  crystals  are  pure  ruby  red, 
wash  them  for  a  moment  or  two  in  a  little  water,  as 
directed  on  page  138,  before  weighing.  When  the 
two  salts  have  been  separately  dissolved,  mix  the  two 
solutions  in  a  stone  bottle  (previously  well  cleaned), 
or  in  a  bottle  encased  in  a  light-tight  tin,  and  keep 
well  corked.  The  mixed  solution  works  better  after 
a  week  or  so  :  giving  a  softer-working  and  more  rapid 
paper.  It  will  keep  in  the  dark  for  a  long  time 
(months),  but  requires  filtering  just  before  use.  This 
is  an  important  point,  and  should  on  no  account  be 
omitted,  even  if  the  solution  has  been  recently  mixed. 
The  filtration  need  only  take  a  minute  or  two,  pro- 
vided a  suitable  filter  paper  and  funnel  is  used,  and 
the  former  properly  fitted  (see  page  119). 

If  a  little  bichromate  of  potash  be  dissolved  in  the 
sensitising  solution — in  the  proportion  of  half  a  grain 
per  ounce  or  one  gram  per  litre — the  paper  will  keep 
considerably  longer  than  if  prepared  with  the  plain 


THE   FERRO-PRUSSIATE   PEOCESS  13 

mixture  ;  but  paper  is  so  very  readily  coated  that 
this  addition  is  not  really  necessary. 

As  explained  in  the  chapter  on  paper,  a  very  great 
variety  of  papers  can  be  coated  with  the  sensitising 
solution,  if  a  good  arrowroot  sizing  be  first  given. 
The  beginner  will  find  it  best  to  use  a  thin  paper 
like  Eives,  which  does  not  absorb  too  much  sensitiser. 
Pin  the  sheets  down  to  a  clean  board,  placing  a  piece 
of  blotting-paper  underneath,  and  coat  the  paper  as 
evenly  as  possible  with  a  fine  Turkish  sponge.  You 
will  find  it  quite  easy  to  give  a  very  uniform  coating. 
Coating  the  paper  must,  of  course,  take  place  by  gas- 
light or  very  weak  daylight,  as  used  for  toning.  The 
paper  must  be  dried  as  quickly  as  possible  in  the 
dark — in  a  drying-cupboard  or  at  a  moderate  distance 
from  the  fire.  It  should  be  kept  as  dry  as  possible. 
As  to  how  long  the  sensitised  paper  will  keep  in  good 
condition,  a  great  deal  depends  on  the  quality  of  the 
paper  and  on  the  sizing.  Good  paper  lightly  sized 
keeps  longest,  whilst  a  low-grade  paper  with  heavy 
sizing  speedily  deteriorates. 

On  exposure  to  light  behind  a  negative,  the  color 
of  the  paper  gradually  changes  through  bluish-green 
and  bluish-grey  to  olive-green.  A  fully  exposed 
print  has  a  choked-up  appearance  in  the  shadows, 
whilst,  with  some  papers,  excessive  over-exposure 
produces  a  peculiar  bleached  appearance  of  the 
shadows.  On  removal  from  the  frame,  the  print 
can  be  kept  for  a  day  or  two,  though  it  is  better  to 
develop  within  a  few  hours. 

Development  consists  in  merely  washing  the  print 
in  water  till  the  soluble   salts   are   removed.     The 


14  FERRIC   AND   HELIOGKAPHIC    PROCESSES 

process  may  be  assisted  by  gently  rubbing  with  a  soft 
sponge.  Many  waters  contain  carbonate  of  lime  in 
solution,  which  gradually  decomposes  Turnbull's  blue, 
so  that  as  short  a  washing  as  possible,  commensurate 
with  removing  the  soluble  salts,  is  to  be  aimed  at. 
Half  an  hour  to  an  hour  in  frequent  changes  is 
ample,  but  with  some  waters  it  is  not  possible  to  give 
this  without  distinctly  weakening  the  prints.  In 
these  cases  a  little  citric  acid  (20  grains  per  pint) 
should  be  added  to  the  wash  waters  to  counteract 
their  alkalinity  ;  then  a  final  washing  in  two  or  three 
changes  of  plain  water.  *  A  paper  which  prints  very 
much  more  quickly,  and  is  just  as  satisfactory  in 
other  ways,  is  made  by  coating  with  a  mixture 
containing  green  ferric  ammonium  citrate  instead 
of  the  red.  This  salt,  the  use  of  which  is  due  to 
Valenta,  can  be  had  from  Merck,  of  Jewin  Street. 
Two  solutions  are  made  as  before  : — 

Ferric  am.  citrate  (green),     110  grains.  250  grams. 

Water,       ....       1  ounce.  1000  c.cs. 

Potass  ferricyanide,     .          .     40  grains.  90  grams. 

Water,       ....       1  ounce.  1000  c.cs. 

Equal  volumes,  mixed  together,  make  the  sensitising 
solution,  which  keeps  just  as  well  as  that  made  with 
red  citrate. 

A  still  more  rapid  paper  is  prepared  in  an  entirely 

*  A  mixture  of  alcohol  (50  parts)  and  water  (950  parts)  is  recom- 
mended by  Hofbauer  {Camera  Obscura,  1899,  p.  288)  in  place 
of  pure  water,  as  giving  prints  with  pure  whites.  For  deep  blue 
shadows,  the  prints  are  transferred  direct  from  the  alcohol  bath 
to  a  2  per  cent,  potass  bichromate  solution.  After  remaining  here 
a  few  minutes  they  are  rinsed  in  1  :  50  acetic  acid  and  dried. 


THE   FERRO-PRUSSIATE   PROCESS  15 

different  way.  Uranic  salts,  when  exposed  to  light, 
are  reduced  to  uranous  salts,  and  if  the  exposure 
takes  place  in  the  presence  of  a  ferric  salt,  the  uran- 
ous salt  reduces  the  ferric  salt  to  the  ferrous  state, 
becoming  itself  thereby  oxidised  back  to  uranic  salt, 
and  ready  to  be  affected  by  light  again.  This  action, 
coupled  with  the  direct  action  of  light  on  ferric  salts, 
confers  upon  paper  coated  with  a  mixture  of  the  two 
salts  a  high  degree  of  sensitiveness.  Papers  prepared 
in  accordance  with  these  facts  were  described  by 
Alleyne  Eeynolds  before  the  Sheffield  Photographic 
Society  in  1889,  but  appear  to  have  attracted  little 
attention.  Eeynolds'  formula  for  coating  was  a 
mixture  of  equal  volumes  of  a  saturated  solution  of 
uranic  chloride  and  a  40  per  cent,  solution  of  ferric 
sodic  oxalate.  A  simpler  formula,  which  the  writer 
finds  to  answer  very  well,  is  : — 

Green  ferric  am.  citrate,     .  110  grains.        250  grams. 
Uranic  nitrate,  ...     35       „  80       „ 

Water,       ....       1  ounce.       1000  c.cs. 

This  is  applied  to  paper  in  the  usual  way,  and 
prints  in  the  frame  to  a  rather  faint  image,  which  is 
developed  on  a  solution  of  potassium  ferricyanide  : — 

Potass  ferricyanide,    .         .     22  grains.  50  grams. 

Water,       ....       1  ounce.       1000  c.cs. 

The  blue  image  at  once  makes  its  appearance,  and  the 
print  has  only  to  be  washed  in  water  in  the  usual  way. 
A  large  number  of  formulae  for  the  ferro-prussiate 
process  have  been  published,  and  while  for  simplicity 
and  certainty  the  writer  can  recommend  the  fore- 
going, one  or  two  others  may  be  added. 


16 


FERRIC  AND  HELIOGRAPHIC  PROCESSES 


88  grains. 

200  grams. 

131       „ 

300       „ 

88       „ 

200       „ 

2  ounces. 

2000  c.cs. 

400  c.cs. 

250  grams. 
1000  c.cs. 


Chambon*  gives  : — 

Gum  arabic, 

Ferric  am.  citrate, 

Tartaric  acid,     . 

Distilled  water, 
Dissolve  completely,  and  add  : — 

Liq.  ammonia,  .   192  mins. 

Shake  well,  and  add  : — 

Potass  ferricyanide,       110  grains. 

Distilled  water,  .       1  ounce. 

Mix  thoroughly,  and  allow  to  stand  "a  quarter  of 
an  hour  before  use.  The  color  of  the  prints  is 
improved  by — 

Eau-de-javelle,t  •     25  mins. 

"Water,      ...       1  ounce. 

followed  by  thorough  washing. 
Lagrange  J  gives  : — 

Ferric  am.  oxalate,    .     44  grains. 

Oxalic  acid,        .         .       4       „ 

Distilled  water,  .       1  ounce. 

Potass  ferricyanide,  .     44  grains. 

Water,      ...       1  ounce. 
Use  equal  parts. 

Other  formulae,  especially  for  engineering  work, 
will  be  found  in  Chapter  X. 

*   The  British  Journal  of  Photography,  16th  Dec.  1898. 

t  Or,  Labarraque's  solution  (sodium  hypochlorite)  is  made  as 
follows : — Shake  up  bleaching  powder  (1  ounce)  with  crystallised 
soda  carbonate  (1J  ounces),  previously  dissolved  in  a  little  water. 
Filter.  Shake  up  undissolved  residue  with  plain  water,  and  again 
filter.  Use  filtrate.  {The  Figures,  Facts,  and  Formula  of  Photog- 
raphy). 

t  Phot.   Wochenblatt,  1887,  p.  418. 


50 

c.cs. 

1000 

)> 

100 

grams. 

10 

>> 

1000 

c.cs. 

100 

grams. 

1000 

c.cs. 

TONING   BLUE   PRINTS  17 


CHAPTEE    II 

Toning  Blue  Prints 

Blue  prints  can  be  toned  to  several  other  colors, 
and  a  large  number  of  formulae  have  been  published 
at  one  time  or  another.  Many  of  these  do  not  come 
within  the  sphere  of  practical  photography,  for  they 
merely  enable  a  tone  to  be  obtained  which  is  very 
frequently  only  a  sorry  apology  for  one  which  can 
be  obtained  much  more  readily  by  some  other 
process.  For  instance,  the  Kallitype  and  Obernetter 
processes  give  dark  rich  tones  very  easily,  and  it  is 
a  mistaken  policy  to  torture  the  blue  ferro-prussiate 
image  with  chemical  reagents,  with  the  object  of 
imitating  these  other  processes. 

The  most  satisfactory  processes  for  altering  the 
color  of  blue  prints  will  now  be  given,  premising 
the  remark  that,  for  success,  the  prints  must  be 
well  washed,  and  have  beeD  made  on  well-sized 
paper,   to  avoid  a  sunken  image. 

Gree7iish-Mack  (Boy's  process). — Make  a  solution 
of— 

Borax, 
Water, 


30  grains. 

70  grams. 

1  ounce. 

1000  ccs. 

2 

18  FERRIC   AND   HELIOGRAPHIC   PROCESSES 

Add  drop  by  drop  sulphuric  acid  till  the  solution 
reddens  litmus-paper.  Then  add  10  per  cent, 
ammonia  solution  until  the  red  color  of  the  litmus- 
paper  just  commences  to  change-;  if  too  much 
ammonia  is  added,  add  one  or  two  drops  more 
sulphuric  acid  and  try  again.  The  liquid  should 
just   show   a   faint   alkaline  reaction.     Now  add — 

Powdered  catechu,    .       4  grains.  10  grams, 

and  shake  well.  Nearly  all  the  catechu  dissolves. 
The  solution  is  filtered  and  is  ready  for  use.  The 
washed  print  is  placed  in  the  above  solution  and 
removed  at  the  stage  desired.  Catechu  occurs  in 
commerce  in  several  varieties,  *  and  the  tone  varies 
with  them,  ranging  from  greenish-blue  to  greenish- 
black.  Keep  the  solution  as  cold  as  possible:  there 
is  then  least  liability  for  the  high-lights  to  become 
stained,  a  defect  of  most  of  the  toning  processes, 
though  less  noticeable  with  catechu  than  with  the 
others.  Wash  the  prints  for  a  few  minutes  after 
toning. 

The  permanency  of  prints  toned  by  Eoy's  process 
— which  the  writer  considers  the  most  satisfactory 
of  all — may  perhaps  be  regarded  by  some  as  some- 
what doubtful.  Catechu,  however,  is  one  of  the 
most  permanent  dyes,  and  the  tone  obtained  may 
be  very  fairly  compared  with  those  of  the  platinum 
prints  toned  by  Packham's  process.  The  latter,  as 
the  experience  of  many  during  the  past  few  years 
has  proved,  may  be  regarded  as  permanent. 

*  The  Photogram,  1896  (Dec),  p.  299. 


TONING   BLUE   PRINTS  19 

Brown  Tone  (Tannin  process). — Place  the  dry 
prints   in — 

Liq.  ammonia  ('880),        6  mins.        12*5  c.cs. 
Water,     ...       1  ounce.     1000    ,, 

As  soon  as  the  color  has  disappeared,  rinse  for  a 
few  minutes  and  transfer  them  to — 

Tannic  acid,      .         .       9  grains.  20  grams. 

Water,      ...       1  ounce.       1000  c.cs. 

In  this  solution  the  prints  will  gradually  assume  a 
brown  color.  The  intensity  of  the  brown  deposit 
is  increased  by  adding  a  drop  or  two  of  the  ammonia 
bath  to  the  tannin  solution,  but  the  procedure  is  apt 
to  cause  stained  high-lights. 

Purple-brown  (Bolle's  Tannin  and  Pyro  process). 
— Make  a  hot  solution  of  tannic  acid  and  add  a  trace 
of  pyrogallic  acid  : — 

Tannic  acid,      .        22-35   grains.    50-80  grams. 
Pyrogallic  acid,  .  Trace.  Trace. 

Water,     ...       1    ounce.       1000  c.cs. 

Immerse  the  print  in  this  for  a  minute  or  two  until 
the  blue  gives  way  to  lilac.  Einse,  and  place  for  a 
moment  or  two  in  a  caustic  potash  solution. 

Caustic  potash,  .  4-9  grains.      10-20  grams. 

Water,     ...       1  ounce.        1000  c.cs. 

The  process  should  be  conducted  as  quickly  as 
possible,  but  a  rose-coloured  tinge  in  the  high-lights 
is  unavoidable,  which,  for  some  subjects,  may  be  an 
improvement. 

Violet-black  (Gallic  Acid  and  Pyro). — Bolle 
recommends    the    following    process,     with   which, 


20  FERKIC   AND   HELIOGRAPHIC   PROCESSES 

however,  the  writer  has  not  been  successful  in 
obtaining  anything  but  weak  and  sickly-looking 
prints.     Place   in — 

Carbonate  of  soda  (cryst.),    22  grains.         50  grams. 
Water,     ....       1  ounce.     1000  c.cs. 

In  this  the  print  changes  to  pale  yellow.  Einse 
slightly,  and  place  in — 

Gallic  acid,        .         .     4    grains.  8  grams. 

Pyrogallic  acid,  .       \  grain  *5  gram. 

Water,  .         .     1    ounce.        1000  c.cs. 

With  gallic  acid  alone,  violet  tones  are  produced, 
whilst,  by  increasing  the  proportion  of  pyro,  a 
blacker   image   results. 

Lilac  (Bolle's  process). — A  lilac  color  is  produced 
by  immersing  the  print  in  a  hot  solution  of  acetate 
of  lead  (sp.  gr.  1*24).  The  prints  are  then  well 
washed.  These  lilac  prints  can  be  toned  still 
further  by  placing  them  in  a  35  per  cent,  solution 
of  potassium  sulphocyanide,  pressing  between  blotting- 
paper,  and  drying  before  a  fire  :  or  a  better  plan  is 
to  add  a  few  drops  of  lead  acetate  solution  to  the 
sulphocyanide,  completing  the  process  as  just 
mentioned,  The  mixed  bath  of  lead  and  sulpho- 
cyanide must  be  made  fresh  for  each  batch  of  prints. 

The  color  has  the  obvious  disadvantage  of  not 
resisting  moisture,  in  the  form  of  perspiration  from 
the  hands,  damp  air,  etc.  The  image,  too,  fades 
appreciably  in  a  strong  light,  and  regains  its  original 
intensity  in  the  dark.  Its  most  useful  application 
seems  to  be  in  toning  blue  transparencies  for  lantern 
slides. 


TONING  BLUE   PRINTS  21 

Black  Tones  {Lagrange' s  process). — "Well  wash  the 
prints,  give  a  final  rinse  in  distilled  water,  and,  in 
a  yellow  light,  bleach  in — 

Silver  nitrate,  .         .       9  grains.  20  grams. 

Distilled  water,         .       1  ounce.        1000  c.cs. 

Well  wash,   first   in  distilled  water,    fume   with 
ammonia,  expose  to  light,  and  develop  with  ferrous 
oxalate  developer. 
Modified  Blue. — 

Sulphuric  acid,  .       4  mins.  8  c.cs. 

Water,     ...       1  ounce.        1000     „ 

gives  a  greenish  tint  to  the  blue. 

Washing  with  some  kinds  of  tap  water  reduces 
the  intensity  of  the  blue  and  at  the  same  time 
modifies  its  color.  Some  hours'  immersion  gives  an 
exceedingly  agreeable  blue,  particularly  for  large 
prints,  for  which,  very  often,  the  ordinary  blue  is 
too  bright. 

According  to  H.  H.  Buckwalter,*  the  following 
process  gives  a  very  pleasing  blue.  Place  the  print 
in  water  for  a  few  seconds,  then  into — 

Liq.  ammonia  (*880),        1  min.  2  c.cs. 

Water,     ...       1  ounce.        1000     ,, 

in  which  it  bleaches  and  turns  a  peculiar  purple. 
When  sufficiently  reduced,  place  direct  into — 

Monsell's  salt,  .         .     27  grains.  62  grams. 

Water,      ...       1  ounce.        1000  c.cs. 

for  about  two  minutes.  Monsell's  salt  is  basic 
ferric  sulphate.  Wash  for  five  minutes  on  removal 
from  the  iron  bath. 

*  Canadian  Photographic  Journal. 


22  FERRIC   AND   HELIOGRAPHIC   PROCESSES 

Brightening  the  Color. — The  blue  color  is  im- 
proved by  several  baths,  applied  after  washing  out 
the  ferricyanide.     One  is — 

Alum,       .         .         .11  grains.  25  grams. 

Water,     ...       1  ounce.       1000  c.cs. 

Another — 

Oxalic  acid,       .         .14  grains.  30  grams. 

Water,      ...       1  ounce.        1000  c.cs. 

Immerse  for  about  thirty  seconds  and  wash  again 
in  water.  Citric,  nitric,  and  other  acids,  potassium 
bisulphate,  bleaching  powder,  all  in  weak  solution, 
are  among  other  reagents  which  answer  the  same 
purpose. 

Intensification  to  a  slight  extent  is  possible  by 
immersion  of  the  prints  in  a  solution  of  an  iron 
salt,  which  intensifies  probably  by  combining  with 
ferricyanide  occluded  by  the  blue  deposit.  Immerse 
in — 

Ferric  chloride,  .       2  grains.  5  grams. 

Water,     ...       1  ounce.       1000  c.cs. 

Reduction  is  a  process  which  is  similarly  limited 
in  its  application.  Long  washing  is  the  most 
successful  reducer  of  slightly  overprinted  proofs.  A 
chemical  reducer  is  : — Immerse  in  a  weak  solution 
of  caustic  potash  till  the  lines  become  clear  and  the 
ground  grey.  Then  transfer  to  weak  hydrochloric 
acid  till  the  blue  color  comes  back  :  then  well  wash. 

Titles,  etc.,  can  be  written  with  the  oxalate 
solution  given  on  page  115. 


THE   USES   OF   BLUE   PRINTS  23 


CHAPTEE   III 

The  Uses  of  Blue  Prints 

Colonel  Baden-Powell  immortalised  ferro-prussiate 
by  issuing  one-pound  notes  produced  by  that  process 
during  the  siege  of  Mafeking.  The  notes  were  from 
'  B.-P.'s '  own  design.  Five  hundred  of  them  were 
issued  and  not  one  presented  for  payment.* 

The  simplicity  of  the  ferro-prussiate  process  will 
at  once  suggest  many  uses  for  it. 

Trial  Prints.  — In  the  first  place,  it  is  eminently 
suited  for  making  trial  prints  from  negatives.  When 
making  the  print,  a  piece  of  paper,  about  half  an 
inch  longer  than  the  negative,  should  be  used,  this 
additional  portion  being  shielded  from  light  during 
printing  by  a  piece  of  opaque  paper.  The  print  is 
thus  obtained  with  a  white  strip  along  one  edge,  on 
which  can  be  written  particulars  of  the  exposure, 
subject,  etc.,  of  the  negative. 

Negative  Register.  — These  prints  bound  together  in 
lots  of  twenty-five  or  fifty  make  a  most  useful  negative 
register.  The  prints  are  numbered  to  coincide  with 
the  negatives  themselves,  and  it  will  be  found  a 
great  convenience  to  be  able  to  turn  up  a  positive 
copy  of  the  negative,  bearing  particulars  of  exposure, 
character  of  negative,  etc. ,  instead  of  looking  up  the 
negative  itself. 

*  Photography,  1900,  p.  569  (Aug.  30). 


24  FERRIC  AND  HELIOGRAPHIC   PROCESSES 

Printing  on  Tour. — To  the  tourist  in  foreign 
countries  who  is  anxious  to  make  prints  of  those 
negatives  which  he  develops  en  route,  the  process  is 
to  be  commended.  He  may  take  a  supply  of  paper 
sealed  up,  but  better  a  small  ruby  bottle  of  sensi- 
tising solution  and  a  small  sponge.  A  few  minutes' 
work,  after  the  development  of  the  negatives  at 
night,  will  place  him  in  possession  of  the  necessary 
paper  on  which  to  print  from  them  the  following 
morning. 

Illustrated  Post  Cards.  — The  same  sensitising  solu- 
tion can  be  called  into  requisition  for  producing  the 
indispensable  illustrated  post  card.  A  sensitising 
solution  which  has  been  specially  recommended  for 
this  purpose  is  as  follows  : — 

Ferric  am.  oxalate,    .     30  grains.  70  grams. 

Ferric  am.  citrate,     .     30       ,,  70       „ 

Water,      ...       1  ounce.       1000  c.cs. 

Sensitise  with  this  solution  and  develop  on — 

Potass  ferricyanide,  .     44  grains.         100  grams. 
Water,     ...       1  ounce.       1000  c.cs. 

The   Kallitype  formula    on   page  42  is   even   more 
suitable  for  this  purpose. 

Transparencies  on  glass  as  well  as  on  paper  are 
within  the  scope  of  the  process ;  the  latter,  par- 
ticularly, are  useful  for  decorative  purposes.  For 
lantern  slides  and  other  glass  transparencies,  glass 
is  cleaned  thoroughly  and  coated  with  a  gelatine 
mixture  : — 

Nelson's  JSTo.  1  gelatine,     22  grains.  50  grams. 

Water,  ...       1  ounce.        1000  c.cs. 


THE  USES   OF   BLUE   PKINTS  25 

Einse  the  gelatine  once  or  twice  with  water,  stand 
it  aside  for  an  hour  or  so,  then  dissolve  in  the  water 
(by  warming  the  two  on  a  water-bath),  and  filter 
hot  through  cotton.  Warm  the  solution  to  about 
130°  F.,  and  pour  over  the  plates.  Place  them  on 
a  cold  horizontal  slab  to  cool,  and,  as  soon  as  set, 
dry,  preferably  in  a  drying  oven. 

Instead  of  coating  plates  with  gelatine,  ordinary 
lantern  plates  can  be  fixed  without  exposure  to 
light,  and  well  washed  ;  or  spoiled  lantern  plates  can 
sometimes  be  used  for  the  purpose,  after  removing 
the  silver  image.  Farmer's  reducer  is  frequently 
recommended  for  this,  but  is  very  liable  to  leave  a 
yellow  stain.     A  better  reagent  is  : — 

Sat.  sol.  of  potass  cyanide  )     ,  _  ,  _ 

r  >    15  mins.  12  ccs. 

in  water,  .  .       J 

Sat.     sol.     of     iodine    in  )       ^ 

alcohol,  .       I  "  4    " 

Water,  .  .         .3  ounces.      1000    „ 

after  which  the  plate  is  well  washed. 

The  plates  are  immersed  for  about  five  minutes  in 
the  sensitising  solution  (page  12),  the  surface  rinsed 
from  sensitiser,  and  dried  in  the  dark.  Printing 
takes  place  in  the  usual  manner,  except  that, 
unless  a  special  opal  transparency  frame  is  used, 
the  process  cannot  be  watched.  It  is  not  difficult, 
however,  to  form  an  idea  of  its  progress  by  lookino- 
through  the  back.  Print  far  deeper  than  for  a 
paper  print,  and  wash  in  water  as  usual. 

Collodion  has  been  recommended  as  a  vehicle  for 


26  FERRIC  AND  HELIOGRAPHIC   PROCESSES 

the  sensitive  iron  salts.*  G.  Ardaseer  gives  the 
following  formula : — 

Pyroxyline  (high  temp.),       120  grains.         7*8  grams. 
Methylated  alcohol  ('820),        6  ounces.       170  c.cs. 
,,  ether,         .         .     5        „  140     „ 

Make  this  a  day  or  two  before  using.  Allow  to 
settle,  and  pour  off  the  clear  collodion.  Edge  the 
plates  with  indiarubber  (in  benzole)  solution,  flow 
the  collodion  over,  and  as  soon  as  set  immerse  in  the 
sensitising  liquid. 

Opals,  matt  or  glazed,  can  be  produced  by  the 
same  methods  given  above  for  glass  positives, 
and,  given  suitable  subjects,  make  very  charming 
ornaments  for  the  shelf  or  bracket. 

Transparencies  on  Paper.  — Print  very  much  deeper 
than  for  an  ordinary  print,  and,  after  washing  and 
drying,  render  translucent  by  one  or  other  of  the 
well-known  methods.  One  of  the  simplest  is  to 
iron  small  pieces  of  paraffin  wax  into  the  print  with 
a  smooth  iron,  hot  enough  to  melt  the  wax.  Pieces 
of  best  paraffin  candle  will  answer,  and  the  process 
can  be  carried  out  by  immersing  the  print  in  the 
melted  wax  more  quickly  than  by  ironing.  To  do 
this,  get  your  workroom  warm  and  place  the  wax 
to  melt  in  a  basin  standing  in  almost  boiling  water. 
Warm  a  zinc  tray  before  the  fire,  make  the  print 
quite  dry,  and  place  in  the  tray.  Quickly  pour  the 
wax  into  the  tray,  and  before  it  sets  remove  the 
print.  If  too  much  wax  is  taken  up,  the  print 
must    be   warmed    before    the    fire,    drained,    and 

*  Photography,  1891,  p.  863  (Dec.  31). 


THE  USES  OF  BLUE  PRINTS  27 

pressed  between  blotting-paper.  Castor-oil,  as 
described  on  page  115,  may  also  be  used,  but  always 
leaves  a  very  slight  greasy  feeling. 

The  trouble  of  waxing  can  be  avoided  by  sensitis- 
ing translucent  paper  (as  used  by  draughtsmen  for 
tracing)  as  recommended  by  Hinsdale  Smith,*  who 
uses  a  brand  of  paper  known  as  '  French  parch- 
ment. '  These  tracing  papers  can  be  obtained  in 
sheets,  20  x  30,  30  x  40,  or  40  X  60  inches,  from  large 
engineering  stations  like  Gill  &  Sons,  Charterhouse 
Street,  E.  C. ,  and  can  be  sensitised  like  ordinary 
papers  by  pinning  to  a  board.  The  transparencies 
when  finished  can  be  mounted  on  glass  or  between 
two  thin  cut-out  mounts. 

Imitation  Tiles. — The  similarity  of  the  color  of 
ferro-prussiate  prints  to  that  of  the  old  Delft  pictures 
makes  them  a  fitting  medium  for  preparing  imitation 
tiles,  as  suggested  by  Oscar  Bolle.  Select  suitable 
bold  and  vigorous  subjects,  and  after  the  prints  are 
completed,  mount  on  glass  or  well-seasoned  wood. 
Next,  size  twice  with  glue  (one  part)  dissolved  in 
water  (10  parts)  and  varnish  with  good  '  oak '  or 
'  church  '  varnish. 

Decorative.  — Many  little  knick-knacks  can  be  orna- 
mented with  blue  prints  made  on  paper,  card,  or  other 
material.  Bookmarks  made  from  slips  of  Whatman's 
rough  drawing-paper  look  very  effective  when  they 
bear  a  neatly  vignetted  landscape,  printed  in  Turn- 
bull's  blue. 

For  newspaper  illustration  work  (where  the  print 
is  to  be  drawn  over  for  reproduction)  a  lightly  printed 
*  Anthony's  International  Annual,  1889-90,  p.  218. 


28  FERRIC   AND   HELIOGRAPHIC   PROCESSES 

blue  print  answers  as  well  as  the  bleaching  process, 
used  with  plain  or  matt-gelatine  paper.  The  drawing 
is  made  with  Indian  ink  and  the  faint  blue  image 
escapes  reproduction  when  the  negative  is  made. 
The  oxalate  of  potash  solution  given  on  page  115 
might,  of  course,  be  used  for  bleaching  a  too  deeply 
impressed  print. 

For  educational  work  in  schools  and  colleges  the 
blue  process  finds  a  place.  Many  lecturers  distribute 
small  prints  of  complicated  diagrams,  etc.,  to  the 
members  of  their  class  for  their  future  study  at  home, 
and  when  the  light  permits  its  use,  the  simplicity 
and  cheapness  of  ferro-prussiate  recommends  it  for 
this  work.  In  dull  weather  gelatino-bromide  must 
be  used,  though  the  uranium  process  (page  15)  is 
worth  a  trial.  Blue  printing  has  been  used  in  the 
New  York  Kindergarten  Schools.  The  children 
are  taught  to  copy  pressed  flowers  and  grasses  in  the 
sun  and  fix  the  impressions  in  water.  * 

In  the  laboratory  the  blue  print  has  been  found 
most  useful  ■f  in  recording  results  of  experiments, 
duplicating  notes,  etc. 

*  New  York  Times,  Apr.  11,  1900. 

t  Chas.  H.  Himes,  Ph.D.,  Photographic  Times,  1896,  p.  187. 


FEKRO-PKUSSIATE   IN  TRI-COLOR   WORK  29 


CHAPTEE   IV 

Ferro-Prussiate  in  Tri-color  Work 

The  pure  blue  color  given  by  the  ferro-prussiate 
process  has  naturally  been  utilised  in  recent  tri- 
color work  by  the  superposition  method.  The 
tri-color  print  by  W.  E.  Brewerton  medalled  at  the 
Royal  Photographic  Society's  exhibition  of  1898, 
had  its  blue  image  in  ferro-prussiate,  and  its  yellow 
and  red  images  in  transparent  inks  by  the  gum- 
bichromate  process.  Mr.  Brewerton  has  kindly 
furnished  the  writer  with  particulars  of  the  method 
employed  by  him,  from  which  the  following  is 
quoted  : — 

' '  Having  produced  our  three  good  negatives,  we 
first  commence  to  print  on  ferro-prussiate  paper 
with  the  negative  taken  through  the  red  screen. 
It  is  very  difficult  to  procure  a  ferro-prussiate  paper 
which  is  suitable  for  the  gum-bichromate  process. 
I  find  a  paper  sold  by  Messrs.  Marion  &  Company, 
in  rolls,  is  the  best  for  the  work  :  it  must,  of  course, 
be  absolutely  fresh.  Care  must  be  taken  not  to 
get  the  blue  print  too  dark,  as  this  will  spoil  the 
finished  work.  Thoroughly  wash  in  several 
changes  of  water,  blot  on  clean  white  blotting- 
paper,    and   immerse  in  a  saturated  solution   of 


30      FERRIC  AND  HELIOGRAPHIC  PROCESSES 

potass  bichromate  (as  used  by  the  Autotype 
Company).  Leave  in  soak  three  minutes,  and 
hang  up  to  dry  in  a  dark  room. 

' '  While  the  blue  print  is  drying,  take  half  an 
ounce  of  '  Stock  solution'  (gum-arabic,  2  ounces  ; 
water,  5  ounces,  prepared  the  day  before),  add  half 
an  ounce  of  water,  and  stir  in  the  red  color,  which 
must  be  thoroughly  ground  with  a  glass  muller. 
The  transparent  photo  colors  of  Messrs.  A.  B. 
Fleming  &  Company  will  be  found  most  excellent 
for  the  process.  Mix  some  of  the  ground  color 
with  the  gum  and  water,  and  stir  well.  The  exact 
proportions  of  color  with  gum  solution  cannot  be 
very  well  given,  as  different  results  require 
different  consistencies,  but  about  one  part  of  color 
to  three  parts  of  gum  solution  is  a  fair  proportion, 
which  practice  will  enable  the  operator  to  vary 
according  to  his  requirements. 

' '  Now  quickly  coat  the  sensitised  surface  of  the 
blue  print  (which  has  been  pinned  down  to  a 
board)  with  the  mixture,  using  a  hog's-hair  brush  : 
the  important  point  is,  get  the  pigment  over  the 
whole  surface  of  the  paper  very  evenly  and  quickly. 
Finish  off  with  a  soft  camel's  or  badger's  hair 
brush.  The  sensitised  paper  is  then  allowed  to 
dry,  which  takes  about  half  an  hour  in  a  warm 
room — of  course,  in  the  dark. 

' '  We  now  take  the  negative  produced  through 
the  green  screen  and  carefully  register  the  print 
upon  it  by  holding  the  two  up  to  the  light — gas  or 
yellow  light  will  do  very  well.     It  may  not  exactly 


FERRO-PRUSSIATE   IN   TRI-COLOR   WORK  31 

register.  If  too  large,  slightly  warm  the  print 
evenly  all  over.  If  too  small,  which  is  usually  the 
case,  pass  it  rapidly  over  the  top  of  a  jug  contain- 
ing hot  water  :  this  will  expand  the  paper  to  its 
proper  size. 

' '  "When  the  print  and  negative  coincide  exactly, 
place  them  in  a  printing  frame  and  expose  to  a 
diffused  light  for  from  fifteen  to  thirty  minutes — 
the  precise  time  can  only  be  found  by  practice. 
Having  printed  the  picture,  place  it  in  cold  water 
face  downwards  for  two  or  three  minutes,  change 
the  water  several  times,  and  commence  the  washing 
away  of  the  soluble  parts.  This,  I  need  hardly  say 
to  those  who  have  used  the  gum  process,  is  the 
most  difficult  part  of  the  proceedings.  Very  great 
care  should  be  taken  in  manipulating  the  print,  and 
many  methods  —  running  water,  sawdust  and 
water,  brushes,  etc. — can  be  used  to  wash  away 
the  soluble  gum  and  color.  I  myself  find  a  piece  of 
cotton-wool  the  most  suitable.  A  rough  print  on 
P.  0.  P.  or  ferro-prussiate  paper  should  always  be 
kept  in  sight,  when  washing  away,  as  a  guide  to 
the  removal  of  the  soluble  parts. 

' '  This  washing  being  completed,  the  double 
print  is  then  before  you  (blue  and  red),  and  often 
presents  a  very  pleasing  appearance.  It  now 
requires  the  yellow  image,  which  is  printed  from 
the  negative  taken  through  the  blue  screen  as  just 
described  for  the  red,  though  I  might  mention  that 
the  yellow  requires  much  less  exposure. ' ' 

Another  tri-color  process  which  may  be  mentioned 


32  FEKRIC  AND  HELIOGRAPHIC   PROCESSES 

is  that  of  Dr  Noack,*  who  prints  the  red  image  first 
by  a  modification  of  Feer-type.  The  paper  is  then 
re-sensitised  with  a  solution  of  lead  ferricyanide,  and 
a  yellow  image  obtained,  after  exposure,  by  treating 
with  potass  bichromate  solution.  Lastly,  the  blue 
image  is  obtained  by  again  sensitising — Valenta's 
formula  (page  14) — followed  by  exposure  and 
washing  in  water.  There  is  considerable  room  for 
improvement  in  this  process,  which,  in  its  present 
state,  presents  many  practical  difficulties. 


CHAPTEE   V 

The  Kallitype  Process 

Theory  in  Brief. — Paper  coated  with  a  mixture 
of  ferric  oxalate  and  silver  nitrate  gives,  on 
exposure  to  light,  an  image  in  ferrous  oxalate, 
which,  on  a  suitable  solvent  of  ferrous  oxalate 
being  applied,  precipitates  an  image  in  metallic 
silver. 

This  process,  which,  it  will  be  seen,  is  on  the 
same  lines  as  Herschel's  '  chrysotype, '  was  patented 
by  W.  W.  J.  Mcolf  in  1889,  and  in  the  original 
form  in  which  it  was  placed  upon  the  market  the 
silver  salt  was  contained  in  the  developer  instead  of 

*  British  Journal  of  Photography,  1898,  page  822  (Dec.  23), 
from  Phot.   Correspondenz. 

t  English  patents   5374  (1889),  4269  (1890),  7312  (1891). 


Brown  Process  Neaci live  Copyr. 


|        ' Perfection" Brand  Paper. 

J  J  Bemrose  &Son$JM.Denhj$Leed$  &>London , 


THE   KALLITYPE  PROCESS  33 

on  the  paper.  The  incorporation  of  the  two  salts 
in  the  sensitive  film,  as  subsequently  patented, 
greatly  simplifies  the  process,  which  is  in  fact  one 
of  the  easiest  to  work,  and  affords  opportunity  for 
obtaining  a  variety  of  tones. 

A    sensitising    solution    which    gives    first-rate 
results  is  that  of  W.  K.   Burton  : — 


Ferric  oxalate, 

75  grains. 

172  grams. 

Silver  nitrate, 

•     30      „ 

69       „ 

Distilled  water, 

1  ounce. 

1000  c.cs. 

Weigh  out  the  ferric  oxalate  and  place  in  a 
stoppered  bottle  :  add  the  water,  place  the  bottle 
in  a  saucepan  of  water,  and  gradually  raise  the 
temperature,  shaking  the  bottle  till  the  ferric 
oxalate  dissolves.  If  it  does  not  do  so,  add  a  little 
oxalic  acid,  say  5  or  10  grains.  Any  ferrous 
oxalate  contained  in  the  ferric  salt  is  left  un- 
dissolved, and  unless  the  liquid  is  quite  clear  the 
solution  should  be  passed  through  a  paper  filter 
(page  119).  Then  add  the  silver  nitrate,  and  store 
in  the  dark.  Instead  of  weighing  out  the  solid 
oxalate,  which  is  a  somewhat  expensive  salt,  the 
solution  of  the  same,  made  as  described  on  page  137, 
can  be  used,  when   the   above   formula  will   stand 


thus 


20  per  cent.  sol. 

ferric  oxalate, 
Silver  nitrate, 
Water  to  make 


410  mins. 

852  c.cs. 

30  grains. 

69  grams, 

1  ounce. 

1000  c.cs. 

A  pure   paper   must   be   used.     Saxe   or   Eives, 
Whatman's    drawing-papers,    and    good    cartridge- 

3 


34  FERRIC   AND   HELIOGRAPHIC   PROCESSES 

papers  are  all  suitable.  It  is  found  that  the  paper 
has  considerable  influence  on  the  tone.  Cartridge- 
papers  give  warm  sepias  with  great  readiness,  but  do 
not  yield  engraving  blacks.  Whatman's  drawing- 
papers,  on  the  other  hand,  do  not  give  a  warm 
brown  at  all  easily. 

Coat  the  paper  (pinned  to  a  board)  with  a  tuft  of 
cotton-wool  or  fine  sponge.  The  writer  prefers  the 
latter.  Squeeze  all  surplus  sensitiser  from  the 
sponge,  and  draw  broad  strokes  across  the  paper, 
afterwards  crossing  the  direction  of  these  to  get  as 
uniform  a  coating  as  possible.  Allow  to  lie  for  a 
minute  or  so  for  the  solution  to  sink  slightly  into 
the  paper.  A  too  superficial  coating  gives  an  image 
which  is  liable  to  be  rubbed  off  in  the  after- 
treatment.  Then  dry  quickly  in  front  of  a  clear 
fire  at  such  distance  that  the  paper  does  not  become 
appreciably  warm  to  the  hands.  Overheating  will 
cause  fog. 

Very  rough  paper  requires  greater  care  in  sensitis- 
ing, to  ensure  the  solution  reaching  the  depressions 
in  the  paper.  Work  in  plenty  of  gas  or  lamp  light, 
and  apply  the  solution  thoroughly  by  dabbing  gently 
with  cotton-wool  (W.  K.  Burton). 

Paper  will  keep  some  days  wrapped  in  paper,  but 
is  best  preserved  in  calcium  chloride  tubes,  in  which 
it  will  keep  for  months. 

Printing  takes  place  rather  more  rapidly  than 
P.O. P.  The  image  makes  its  appearance  in  the 
same  manner  as  in  the  platinotype  process,  though 
exposure  is  complete  when  a  rather  less  vigorous  image 
of  the  shadows  is  produced.      Detail  at  this  point 


THE  KALLITYPE  PROCESS  35 

should  be  faintly  visible  in  the  densest  portions  of 
the  negatives  in  bluish-brown  on  the  pure  yellow 
ground.  Keep  the  paper  dry  during  printing  by 
backing  with  oil-cloth  or  rubber.  Damp  paper 
makes  it  difficult  to  judge  when  exposure  is  correct. 
If  kept  dry  the  paper  can  be  stored  for  a  reasonable 
time  before  development. 
Developer  for  Black  Tones.  — 


Borax,    . 

44  grains.         100  grams. 

Rochelle  salt, 

33       ,,               75       ,, 

Water,  . 

1  ounce.        1000  c.cs. 

Potass  bichromate  ) 
sol.  (1  per  cent.) ) 

45-55  mins.     94-115    „ 

The  bichromate  solution  contains  : — 

Potass  bichromate, . 

4 J  grains.         10  grams. 

Water  to  make 

1    ounce.      1000  c.cs. 

Its  action  is  to  restrain,  and  its  quantity  can  be 
adjusted  to  suit  different  types  of  negatives.  Too 
little  bichromate  causes  muddy  prints  with  stained 
high-lights  ;  too  much  destroys  the  half-tone. 

Immerse  the  print  face  up  in  this  solution  and 
remove  any  air  bubbles  with  the  finger  or  a  piece  of 
glass  rod.  The  image  attains  its  full  depth  in  a  few 
seconds,  but  the  prints  must  be  allowed  to  remain 
from  fifteen  minutes  (at  least)  to  half  an  hour,  in 
order  to  completely  dissolve  all  iron  salts  in  the 
paper.  Neglect  of  this  is  the  cause  of  yellow  stains 
in  the  finished  prints.  Do  not  overwork  the  develop- 
ing baths,  or  the  vigour  and  color  of  the  prints  will 
suffer.     Ten  ounces  (300  c.cs.)  will  develop  five  to 


36 


FERRIC   AND   HELIOGRAPHIC   PROCESSES 


six  dozen  half-plates.  When  not  in  use,  keep  the 
baths  in  the  dark. 

Hough-surfaced  prints  must  not  be  rubbed  over 
each  other  in  the  developing  or  other  baths  :  the 
friction  of  one  rough  surface  over  another  is  liable 
to  rub  off  the  silver  image,  causing  a  mottled 
appearance  of  the  print  (W.   K.   Burton). 

Developer  for  Purple. — 

Borax, 

Rochelle  salt, 
Water, 

Potass  bichromate, 
1  per  cent.  sol. 

Developer  for  Sepia. 

Rochelle  salt,  . 
Water,     . 

Potass  bichromate,  ) 
1  per  cent.  sol.    J 

Developer  for  Maroon  Tones.  — The  following  has 
been  recommended  : — 

Rochelle  salt,   . 
Sodium  tungstate,    . 
Water,     . 

Fixing  Solution. — 

Hypo,      . 

Liq.  ammonia  ("880), 

Water,     . 

Hypo  was  not  recommended  for  fixing  in  Nicol's 
original  process,  but  later  experience  has  shown 
that  it  is  advisable  on  the  score  of  permanency. 


12  grains. 

28  grams. 

44 

^^             51 

100      „ 

1  ounce. 

1000  c.cs. 

45- 

-55  mins. 

94-115     „ 

22  grains. 

50  grams. 

1  ounce. 

1000  c.cs. 

25- 

-30  mins. 

52-62  „ 

44  grains. 

100  grams. 

22 

-J-J             55 

50^   „ 

1  ounce. 

1000  c.cs. 

1  ounce. 

200  grams. 

120  mins. 

12  c.cs. 

20  ounces. 

1000    „ 

The  kallitype  process 


37 


The  prints  are  transferred  direct  from  the 
developer  into  this  bath,  and  are  turned  over 
frequently  for  ten  minutes  ;  they  are  then  given  a 
similar  treatment  in  a  second  bath  for  the  same 
time.  Fixing  being  thus  completed,  they  are 
washed  in  running  water  for  about  a  quarter  of  an 
hour  and  dried. 

Engraving  black  tones  are  obtained  by  developing 
with  sodium  acetate,  followed  by  a  solution  of 
potassium  oxalate,   to  render  the  iron  soluble. 

Developer.  — 

Sodium  acetate,        .  66  grains.  150  grams. 

Water,     ...  1  ounce.         1000  c.cs. 

Oxalate  Bath. — 

Potass  oxalate,  .  80  grains.  183  grams. 

Water,     .  .  1  ounce.        1000  c.cs. 

Wash  for  a  few  mintes  in  several  changes,  and  fix 
in  ammonia  solution  as  before. 

Henry  Hall  *  recommends  the  following  f orrnulse 
for  Kallitype : — 
Stock  solutions  for  sensitisers.  — 

A.  Ferric  oxalate,  . 
Distilled  -water,  . 
Picked  gum  arabic, 

B.  Ferric  potass  oxalate, 
Distilled  water,  . 

C.  Oxalic  acid, 
Distilled  water, 
Ammonia  ("880), 

D.  Potass  bichromate, 
Distilled  water,  . 

*  The  Photo- Miniature,  No.  47 


1  ounce. 

200  grams 

5  ounces. 

1000  c.cs. 

.    48  grains. 

22  grams. 

\  ounce. 

62-5      „ 

8  ounces. 

1000  c.cs. 

\  ounce. 

125  grams. 

4  ounces. 

1000  c.cs. 

.   100  minims. 

50    „ 

.  120  grains. 

70  grams. 

4  ounces. 

1000  c.cs. 

38  FERRIC   AND   HELIOGRAPHIC   PROCESSES 

For  average  negatives  mix  A,  1  oz.  ;  B,  \  oz.  ; 
C,  30  minims ;  D,  4  drops.  The  sensitiser  is  made 
from  this  mixture  by  adding  6  grains  of  silver  nitrate 
to  120  minims  of  it.  For  contrasty  negatives,  omit 
D  and  increase  B  and  C,  the  latter  by  not  more  than 
20  per  cent.  (i.e.  to  36  minims),  or  fogging  is  apt  to 
result.  B  can  be  doubled  without  ill  effect,  and  if 
this  is  done  another  grain  of  silver  nitrate  should 
be  added. 

For  very  thin  and  soft  negatives  increase  D — to 
double  in  bad  cases,  at  the  same  time  reducing  C  by 
one  half  or  more. 

Developer. — Sodium  acetate  solution  (1  in  7|  of 
water)  8  ounces  (1000  c.cs.)  ;  tartaric  acid,  12  grains 
(3"1  grams);  solution  D,  10  to  100  minims  (2 "5  to 
25  c.cs). 

Clearing  Bath  for  acetate  developed  prints  : — 


Sodium  citrate, 

^  ounce. 

31  grams. 

Citric  acid,    • 

.     20     grains. 

5-5       „ 

Water, 

8    ounces. 

1000  c.cs. 

If  the  borax  and  Eochelle  salt  developer  is  used 
the  following  clearing  bath  is  used  : — 


Rochelle  salt, 

2J  ounces. 

80  grams, 

Rain  water,    . 

32 

1000  ccs. 

Solution  D  (bichromate), 

\  ounce. 

8  grams, 

The  prints  are  treated  in  these  clearing  baths  for 
thirty  minutes. 

The  prints  are  thoroughly  washed  after  the  clearing 
bath — the  function  of  which  is  to  render  the  iron 


THE   KALLITYPE   PEOCESS  39 

salts  thus  removable  by  the  water — and  then  fixed 
for  ten  minutes  in  : — 

Hypo,         ...  1  ounce.         50  grams. 

Water,        ...       20  ounces.    1000  ccs. 
Ammonia  ('880),         .     120  minims.      12     „ 

Print-out  Kallitype  was  patented  by  Nicol  (potass 
oxalate  being  included  in  the  sensitising  solution), 
but  has  not  been  at  all  used.  Brooke*  has  given 
formulae  and  directions. 

Reducing  Kallitypes. — As  the  image  is  a  silver  one, 
Kallitypes  are  amenable  to  the  ordinary  '  reducer. ' 
Hall,f  however,  prefers  a  weak  solution  of  hydro- 
bromic  acid  (35  minims  of  the  strong  commercial 
acid  in  1  ounce  of  water).  It  is  kept  moving  for  a 
minute  or  two  over  the  print,  which  is  then  given 
several  quick  changes  of  water  and  dried. 

For  correcting  prints  lacking  in  pluck  the  hydro- 
bromic  acid  solution  is  applied  for  a  short  time,  the 
prints  rinsed,  fixed  in  hypo  solution  for  five  minutes, 
and  washed  and  dried. 

After-treatment  of  Kallitypes. — The  prints  can  be 
bleached  in — 

Hydrochloric   acid  I         ,ft     .  on 

J  >        10  mms.  20  ccs. 

(sp.  gr.  1-2),        J 

Water,    ...  1  ounce.        1000    ,, 

well  washed,  exposed  to  light,   and  developed  with 
metol  or  other  developer.      Strong  developer  gives 

*  Photography,  1895,  p.  778  (Dec.  5). 
t  The  Photo-Miniature,  No.  47. 


40  FERRIC  AND   HELIOGRAPHIC   PROCESSES 

black  tones  ;  a  weak  one,  warm  tones  (red-brown, 
etc.),  which  can  be  further  changed  to  purple  in  a 
sulphocyanide  toning  bath,  single  or  combined. 

The  original  warm-toned  Kallitypes  can  be  toned 
in  gold  baths,  of  which  that  recommended  by  Dr. 
Frederick  *  is  the  most  noteworthy  : — Water,  8 
ounces  ;  hypo,  1  ounce  ;  gold  chloride,  1  grain. 

For  toning  with  platinum  use  the  following 
bath  : — 


Potass  chloroplatinite, 

f  grain. 

1*7  grams. 

Citric  acid, 

i    » 

•6      „ 

Water,     . 

1    ounce. 

1000  c.cs. 

Uranium  toning  can  also  be  applied  successfully 
to  Kallitype  prints,  if  due  care  be  taken  to  thoroughly 
remove  all  soluble  iron  salts. 

These  after-processes,  however,  are  not  of  much 
importance.  The  chief  claims  of  Kallitype  are  the 
ease  and  directness  with  which  it  gives  prints  in 
metallic  silver   free  from  gelatine  or  other  vehicle. 

A  modification  of  Kallitype  is  used  considerably 
on  the  Continent ;  although  the  results  do  not  at  all 
approach  those  by  the  methods  already  given,  the 
process  is  more  akin  to  the  '  Sepia '  paper  described 
in  another  chapter.  Under  various  fancy  names  it 
appears  on  the  market — as  '  Simili-platinum '  and 
other  papers,  and  as  single  sensitising  solutions.  The 
following  formulae  for  a  paper  and  a  sensitiser  are  as 
good  as  any. 

To  prepare  the  paper,  first  make  the  following- 
stock  solutions  : — 

*   The  Photo -Miniature,  No.  47. 


THE   KALLITYPE   PROCESS 


41 


A. 

Green  ferric  ammo- 
nium citrate,  . 

>    110  grains. 

2*5  grams. 

Water, 

1  ounce. 

1000  c.cs. 

B. 

Tartaric  acid,    . 

18  grains. 

4  grams. 

Water, 

1  ounce. 

100  c.cs. 

C. 

Silver  nitrate,  . 

45  grains. 

10  grams. 

Water, 

1  ounce. 

100  c.cs. 

D. 

Gelatine,  . 

30  grains. 

7  grams. 

Water, 

1  ounce. 

100  c.cs. 

Distilled  water  is  best  used  throughout,  but  certainly 
for  C.  A  and  C  will  keep  for  months  in  the  dark  ; 
B  for  a  week  or  so  only,  unless  a  little  carbolic  acid 
is  added,  but  it  is  better  to  use  it  without  this  addition. 
The  gelatine  solution  should  be  made  at  the  time  of 
use.  The  gelatine  is  first  allowed  to  swell  in  a  portion 
of  the  water  for  half  an  hour,  and  is  then  dissolved  by 
adding  the  remainder  and  placing  the  vessel  contain- 
ing the  whole  mixture  in  a  pot  of  boiling  water. 

To  compound  the  sensitising  mixture  we  mix  equal 
parts  of  these  four  solutions  (say,  1  dram  each)  as 
follows  : — If  the  gelatine  solution  has  set,  place  it  in 
warm  water  until  fluid,  pour  out  into  a  shallow  cup, 
likewise  standing  in  warm  water.  Now  add  A  and 
B,  and  lastly — a  few  drops  at  a  time  and  stirring  all 
the  time  with  a  bit  of  glass  rod — the  silver  nitrate 
solution  C.  The  mixture  is  kept  lukewarm  and 
mopped  all  over  the  paper,  which  is  laid  on  a  bit  of 
board  a  little  smaller  than  itself.  There  is  then  no 
margin  of  board  from  which  dirt  can  be  picked  up 
during  coating.  Use  a  piece  of  cotton-wool  to  apply 
the  liquid,  dabbing  the  solution  quickly  all  over,  and 
at  once  proceeding  to  even  up  the  coating  with  a  flat 


42  FERRIC   AND   HELIOGRAPHIC   PROCESSES 

camel' s-hair  brush,  go  over  the  surface  lightly,  first 
one  way  across  the  paper  and  then  the  other.  The 
brush  should  not  be  pressed  or  rubbed  on  the  paper, 
but  just  dragged  to  and  fro,  holding  it  loosely  between 
the  thumb  and  finger.  As  soon  as  the  coating  begins 
to  look  dull  or  matt,  hang  up  to  dry.  In  summer, 
paper  should  dry  in  a  few  minutes,  but  in  winter  it 
is  well  to  place  it  some  feet  from  a  fire,  not  near 
enough,  of  course,  to  scorch  it.  Both  sensitising  and 
drying  should  be  done  in  a  dim  light.  A  room  by 
gaslight,  or  rather  darker  than  as  used  for  toning 
P.  0.  P. ,  is  a  safe  place. 

The  negative  is  printed  until  a  fairly  vigorous 
image  is  obtained  in  which  the  details  in  the  high- 
lights of  the  original  begin  to  be  apparent.  The  print 
is  developed  by  placing  in  plain  water  for  about  two 
minutes,  in  which  it  takes  on  a  reddish-brown  color. 
It  is  then  transferred  to  a  solution  of  sodium  thio- 
sulphate  (hypo)  for  a  minute  or  two — hypo,  10  grains  ; 
water,  1  ounce  (20  grams  per  litre). 

Here  the  print  becomes  brown  in  color  and  loses 
slightly  in  density.  If  allowed  to  remain  too  long, 
or  if  too  strong  hypo  is  used,  the  loss  in  density 
becomes  appreciable.  Washing  for  an  hour  or  so 
completes  the  process.  The  method  does  not  render 
fine  gradations  well  :  it  requires  a  fairly  strong 
negative. 

The  single  solution  sensitiser  is  made  as  follows  : — 
Dissolve  55  grains  (3  "5  grams)  of  silver  nitrate  in  4 
to  5  drams  (about  15  c.cs.)  of  distilled  water,  and  add 
ammonia  drop  by  drop  until  the  white  precipitate 
first  formed  is  redissolved.     Now  add,  drop  by  drop, 


THE  KALLITYPE  PROCESS  43 

dilute  sulphuric  acid  with  constant  stirring  until  the 
odour  of  the  ammonia  almost  entirely  disappears. 
Forty  grains  (2  "6  grams)  of  green  ferric  ammonium 
citrate  are  now  dissolved  in  6  drams  (20  c.cs.)  of 
water  and  mixed  with  the  silver  solution.  This 
liquid  keeps  well  in  a  stoppered  bottle  in  the 
dark.  A  tin  canister  is  a  convenient  case  in  which 
to  store  the  bottle  containing  it.  Brush  over  the 
paper  as  already  described,  print  as  before,  and  fix 
in  the  following  bath  : — 

Hypo,     .         .         .    100-150  grains.    30-45  grams. 
Soda  sulphite,  .      30-100       „         10-30      „ 

"Water,    ...  7  ounces.       1000  c.cs. 

The  exact  strength  does  not  matter  :  it  is  near 
enough  if  it  falls  between  the  two  quantities  named 
in  the  formula. 

Kallitype  for  Newspaper  Work.  — Kallitype  prints 
have  been  used  for  preparing  drawings  for  process 
reproduction.  A  print  is  taken  in  sunlight  or  by 
the  electric  arc,  developed,  fixed,  washed,  pasted  on 
a  sheet  of  glass,  and  dried.  The  lines  are  put  in 
with  waterproof  Indian  ink  and  the  print  bleached 
with  bichloride  of  mercury.  When  finished  with, 
the  print  is  removed  from  the  glass  by  soaking  in 
water. 

Permanency  of  Kallitype. — The  fact  that  the 
chemical  rationale  of  Kallitype  printing  favours  the 
conclusion  that  the  image  is  metallic  silver  has  been 
assumed  by  some  writers  as  sufficient  guarantee  of 
its  permanency.  It  should,  however,  be  borne  in 
mind  that  when  in  a  finely-divided  condition  silver, 


44  FERRIC   AND   HELIOGRAPHTC   PROCESSES 

like  platinum,  is  apt  to  carry  down  certain  com- 
pounds of  iron,  to  which  very  often  the  color  of  the 
deposited  metal  is  due.  The  criticisms  passed  on 
Carey  Lea's  work  on  the  so-called  alio  tropic  forms 
of  silver  will  call  to  mind  this  characteristic  property 
of  the  finely-divided  metal.  In  the  case  of  platinum 
prints  no  reaction  between  the  iron  and  the  plati- 
num need  be  feared,  but  silver  is  a  metal  more 
susceptible  to  chemical  change,  and  it  is  possible 
that  it  may  undergo  gradual  oxidation  by  traces 
of  associated  ferric  salt.  There  is  no  doubt  that 
numbers  of  Kallitype  prints  have  stood  the  test  of 
time  for  six  years  or  more,  whilst  others  have  faded. 
Hence  the  task  of  obtaining  permanent  prints 
resolves  itself  into  the  complete  removal  of  iron 
salts  from  the  paper,  and  attention  is  therefore 
best  directed  to  the  proper  sizing  of  the  paper,  with 
a  view  to  prevent  the  iron  salt  attaching  itself  to 
the  fibre  of  the  paper,  and  to  a  thorough  treatment 
with  alkaline  and  neutral  solvents  of  iron  salts. 
Experience  shows  that  an  ammonia  fixing  bath  is 
not  sufficient  to  guarantee  permanency,  and  the' 
hypo  bath,  preceded  by  the  thorough  removal  of  the 
iron  salts,  should  be  adopted  from  the  practice  of 
Hall  and  other  later  workers  of  the  process.  Toning 
with  gold  or  platinum  may,  of  course,  be  done,  but 
the  simplicity  and  cheapness  of  Kallitype  is  at  once 
discounted,  and  one  might  as  well  use  platinotype 
right  away. 


THE   OBERNETTER   PROCESS  45 


CHAPTEK    VI 

The  Obernetter  Process 

Theory  in  Brief.  — Paper  is  coated  with  a  mixture 
of  ferric  and  cupric  chlorides.  The  former  of 
these  is  reduced  on  exposure  to  light  to  ferrous 
chloride.  In  the  presence  of  moisture  the  ferrous 
chloride  reduces  the  copper  salt  to  cuprous  chlor- 
ide (Cu2Cl2).  On  immersion  in  potassium  sulpho- 
cyanide  solution,  cuprous  sulphocyanide  (white) 
takes  the  place  of  the  cuprous  chloride.  After 
washing  out  the  excess  of  salts,  the  white  image 
is  developed  with  potassium  ferricyanide  or  other 
reagents. 

This  process,  which  takes  its  name  from  its 
inventor,  J.  B.  Obernetter,  was  published  in  1864, 
and  gives  quite  easily  a  variety  of  tones  which  there 
is  very  good  reason  to  regard  as  permanent. 

Obernetter 's  original  formula  for  coating  the  paper 
is  : — 

Copper  chloride,         .         .         .  100  parts. 

Ferric  chloride  sol.  (sp.  gr.  1*5),  13      „ 

Hydrochloric  acid,      .         .         .  12      „ 

Water,       .         .         .         .         .  1000      „ 

The  writer  prefers  to  increase  the  proportion  of 
ferric  chloride  in  the  above  formula.     A   paper   is 


46  FERRIC   AND   HELIOGRAPHIC   PROCESSES 

thereby  obtained  which  gives  a  more  visible  image 
and  yields  prints  of  greater  vigour. 

A  suitable  proportion  is  30  grams  of  anhydrous 
ferric  chloride  (46  c.  cs.  of  B.  P.  *  sol. ,  sp.  gr.  1  '42). 
The  modified  formula  is  as  follows  : — 


Ferric  chloride  (B.P.  )     00 
sol.,  sp.  gr.  1'42),    J 

46  c.cs. 

Copper  chloride,         .     44  grains. 

100  grams, 

Hydrochloric  acid,      .       5  mins. 

10  c.cs. 

Water,      ...        1  ounce. 

1000    „ 

A  strong  paper,  such  as  Steinbach  ferro-prussiate, 
should  be  used  and  should  be  well  sized.  A  solution 
of  gum-arabic  (10  grains  per  ounce  or  23  grams  per 
litre)  brushed  over,  answers  well.  The  paper  is 
floated  for  two  minutes  on  the  above  solution  and 
dried  in  artificial  light.  The  paper,  which  is  not  so 
sensitive  as  albumen  paper,  keeps  very  well  indeed 
before  exposure.  It  is  printed  until  a  very  faint 
image  appears,  it  being  rather  more  difficult  to 
judge  the  right  point  than  in  platinotype  printing. 
Development  must  follow  exposure  as  soon  as 
possible,  within  two  hours  at  the  latest.  If  longer 
than  this  elapses,  the  cuprous  chloride  gradually 
reverts  to  the  state  of  higher  oxidation,  and  after 
twenty-four  hours  the  paper  can  be  exposed  afresh. 

The  developer  contains  : — 

Potass  sulphocyanide,       5 
Sulphuric  acid  (cone),        \ 
Sensitising  solution,      5-6 
Water,     ...         1 

*  B.P.  =  British  Pharmacopoeia. 


grains. 

12  grams. 

min. 

•5  c.cs. 

mins. 

10-12    „ 

ounce. 

1000    „ 

THE   OBEENETTER   PROCESS  47 

This  forms  a  deep  red  solution  which  deposits  a 
small  precipitate  after  standing  some  time.  This 
may  be  neglected  and  the  clear  solution  decanted 
for  use.  The  developer  can  be  used  over  and  over 
again. 

Float  the  paper  for  three  or  four  minutes,  face 
down,  then  gently  immerse  :  float  the  next,  agitat- 
ing the  liquid  as  little  as  possible  during  these 
operations.  The  prints  may  be  immersed  for  from 
five  minutes  to  half  an  hour.  When  all  have  been 
treated,  transfer  to  a  dish  of  clean  water  and  wash 
in  running  water  for  an  hour.  A  very  faint  image 
is  visible  on  removal  from  the  sulphocyanide  bath, 
but  this  almost  entirely  disappears  on  washing.  At 
this  stage  of  the  process  the  prints  may  be  dried  and 
put  away  until  convenient  to  make  the  image  visible 
by  the  action  of  the  next  bath. 

Potass  ferricyanide,  .        44  grains.  100  grams. 

Water,     ...  1  ounce.  1000  c.cs. 

This  solution  gives  a  red  or  terra-cotta  colored 
print.  It  acts  only  slowly,  but  the  prints  require 
no  attention.  An  immersion  of  several  hours  does 
no  harm,  and  is,  in  fact,  generally  necessary. 
When  the  desired  tone  and  intensity  is  reached, 
wash  in  running  water  for  a  quarter  of  an  hour  or 
so,  and  dry. 

The  red  prints,  thus  produced  by  ferricyanide, 
can  be  further  toned  through  a  series  of  tints  by 
immersion  in  an  acid-iron  solution.  To  insure  the 
success  of   the  toning  process,   the  prints   must   be 


48  FERRIC   AND   HELIOGRAPHIC   PROCESSES 

thoroughly  washed  free  from  ferricyanide,  or   blue 
stains  result.     The  toning  solution  is  : — 

Ferric  chloride  (cryst.),      57  grains.  130  grams 

Ferrous  sulphate,  .145      „  330      „ 

Hydrochloric  acid,        .123      „  280      ,, 

Water,         ...        1  ounce.  1000  c.cs. 

In  this  bath  the  red  tone  gradually  passes  through 
reddish-violet,  blue-violet,  and  black  to  greenish- 
black.  The  prints  are  then  washed  in  one  or  two 
changes  of  water,  acidulated  with  hydrochloric  acid, 
then  in  plain  water,  and  dried.  It  need  hardly  be 
said  that  the  greatest  care  must  be  exercised  in 
keeping  the  last  quoted  solution  and  the  ferricyanide 
separate.  Traces  of  one  carried  into  the  other  on 
fingers  or  prints  will  produce  blue  stains  wholesale. 
The  strongly  acid  character  of  the  toning  bath 
necessitates  a  stout  paper  and  careful  handling. 

A  purple-violet  tone  resembling  a  silver  print  is 
produced  by  washing  the  prints  for  a  minute  or 
two  from  the  iron  solution  and  placing  them  for  a 
few  seconds  in  a  very  weak  solution  of  acetate  of 
lead. 

Other  tones  can  be  obtained  (after  washing  out 
the  ruddy  developer  or  sulphocyanide  of  iron)  by 
silver  nitrate  and  by  permanganate  of  potash.  The 
former  is  used  in  weak  (2  per  cent.)  solution  and 
gives  a  cold  black  image,  the  print  being  after- 
wards fixed  in  water  containing  a  little  oxalate  of 
ammonium.  The  exposure,  for  development  with 
silver  nitrate,  must  be  much  shorter ;  the  exact 
point  is  rather  difficult  to  hit, 


BJa ck Line  Copy .  Wafer  Bath  Development. 


"Perfection" Brand  Paper. 
Bemrose  6>SonSyZ^.I)ei^^leeds  ^London 


THE  URANOTYPE   PROCESS  49 

Potassium  permanganate  is  dissolved  in  water  and 
a  few  drops  of  ammonia  added.  The  strength  of  the 
mixture  is  not  very  important,  and  the  bath  gives 
brown  tones.  The  writer's  experience  is  that  the 
ferricyanide  and  iron  toning  baths  are  preferable  to 
either  of  the  two  last  named. 


CHAPTER    VII 

The  Uranotype  Process 

Theory  in  Brief. — Uranic  salts  exposed  to  light 
yield  uranous  salt,  which  gives,  with  potassic 
ferricyanide,  a  red  image  of  uranous  ferricyanide. 

The  use  of  uranium  salts  for  printing  dates  back 
to  the  very  early  days  of  photography,  but  uranium 
processes  have  never  come  into  extended  use.  A 
uranium  paper  was  formerly  on  the  market,  but  at 
present,  so  far  as  the  writer  knows,  no  paper  of  this 
kind  is  commercially  obtainable. 

The  ordinary  uranium  process  is,  however,  very 
simple,  and  easily  gives  certain  colored  images.  The 
sensitising  solution  is  : — 

Uranium  nitrate,         88  grains.         200  grams. 
Water  to  make,       .       1  ounce.        1000  c.cs. 

Paper   is   floated   on   this   solution   for    about    five 
minutes,    and   dried   before   the   fire  as  quickly  as 

4 


50  FERRIC   AND   HELIOGRAPHIC   PROCESSES 

possible.     The  pale  lemon-colored  paper  must  be  kept 
quite  dry  by  storage  in  a  calcium  tube. 

Uranotype  requires  a  vigorous,  even  hard,  negative. 
It  is  useless  to  expect  good  results  from  a  thin,  flat 
negative,  and  printing  should  be  carried  out  in  sun- 
light to  get  the  best  results.  The  uranium  image — 
purplish-brown — is  much  more  visible  than  that 
obtained  with  Kallitype  or  platinotype,  and  it  is 
quite  easy  to  judge  when  exposure  is  complete.  The 
exposed  paper,  however,  possesses  the  peculiarity  of 
gradually  losing  its  image  when  kept  in  the  dark, 
so  that  it  is  obvious  that  development  must  follow 
exposure  fairly  soon,  and  that  over-exposure  can  be 
readily  corrected. 

Preliminary  Washing. — Before  development  with 
ferricyanide,  the  paper  is  washed  for  ten  minutes  or 
so  in  several  changes  of  water.  Those  who  have 
used  uranium  for  toning  bromide  prints  will  know 
that  the  use  of  a  current  of  water  for  washing  is 
liable  to  give  rise  to  patchy  prints,  and  that  there- 
fore moving  the  prints  in  a  dish  of  still  water  is 
preferable  to  more  energetic  treatment  in  a  print 
washer.  This  washing  being  completed,  the  print 
is  ready  for  development. 
Developer.  — 

Potass  ferricyanide,     55  grains.         125  grams. 
Water,  ...       1  ounce.        1000  c.cs. 

The  prints  can  be^  immersed  in  this  developer,  or  it 
can  be  applied  with  a  camel-hair  mop  or  tuft  of 
cotton-wool.  The  print  develops  in  a  few  seconds  to 
a  clear  Bartolozzi  red. 


THE  URANOTYPE  PROCESS  51 

Final  Washing. — Ten  minutes'  washing  in  several 
changes  of  water  completes  the  process,  so  far  as  the 
red  print  is  concerned. 

Toning  the  Bed  Print.  — The  red  uranium  image  is 
amenable  to  considerable  treatment  with  iron  and 
cobalt  salts,  and  yields,  according  to  the  precise  pro- 
cess adopted,  prints  in  sepia,  green,  or  blue. 

Sepia  and  Green. — 


Cobalt  nitrate, 

30  grains. 

69  grams. 

Ferrous  sulphate,    . 

90      „ 

206      „ 

Water,  . 

1  ounce. 

1000  c.cs. 

In  this  solution  the  washed  red  print  rapidly  passes 
from  red,  through  sepia,  to  green.  To  obtain  inter- 
mediate colors  it  is  necessary  to  remove  the  print 
at  once  and  to  plunge  it  into  a  large  dish  of  water. 
Then  it  is  washed  for  a  minute  or  two,  changing  once 
or  twice,  pressed  between  blotting-paper,  and  dried 
before  the  fire. 

Another  bath  recommended  for  green  tones  is  : — 


Cobalt  nitrate, 

1^  grains. 

3  grams, 

Ferrous  sulphate,   . 

3        „ 

7      „ 

Citric  acid, 

12        „ 

28      „ 

Water,  . 

1    ounce. 

1000  c.cs. 

in  which  the  prints  are  allowed  to  remain  all  night. 
Blue  Prints. — Immerse  in — 


Ferrous  sulphate, 

.  100  grains. 

230  grams 

Nitric  acid,     . 

8  mins. 

17  c.cs. 

Water,  . 

10  ounces. 

1000    „ 

Fixing.  — Prints  which  have  been  toned  in  either  of 


52  FEEKIC   AND   HELIOGKAPHIC   PROCESSES 

the  three  foregoing  baths  must  be  afterwards  passed 
into  a  fixing  bath  of — 

Citric  acid,     .         .     44  grains.         100  grams. 
Water,  ...       1  ounce.        1000  c.cs. 

where  the}7  remain  for  ten  minutes.     Twenty  minutes' 
washing  in  several  changes  completes  the  process. 

Purple  Tones. — Instead  of  developing  with  ferri- 
cyanide,  chloride  of  gold  can  be  used  to  produce  an 
image  of  metallic  gold.  The  prints  must  be  deeply 
printed,  washed  as  usual,  and  developed  in — 

Gold  chloride,         .       4  grains.  *25  grams. 

Water,  ...       1  ounce.  30  c.cs. 

This  is  followed  by  several  minutes'  washing. 
.   Local  development  with  ferricyanide  solution  can 
be  carried  out  just  as  in  platinotype  by  thickening 
the  solution  with  glycerine. 


PRINTS   ON   FABRICS  53 


CHAPTEE    VIII 

Prints  on  Fabrics — Prints  in  Dyes 

Silk,  Nainsook  muslin,  fine  linen  and  cotton  fabrics 
can  each  be  used  as  a  support  for  the  sensitive  coat- 
ing, and,  besides  offering  facilities  for  pictorial  effect 
in  large  sizes,  make  it  possible  to  turn  out  decorative 
articles  of  domestic  use  such  as  d'oyleys,  mats,  anti- 
macassars. 

The  fabrics  should  be  as  pure  as  possible.  Many- 
low  grades  of  silk  are  so  weighted  with  mineral  matter 
as  to  make  them  quite  unsuitable.  Purchase  a  fine 
quality  silk  and  wash  thoroughly  in  hot  water  ; 
allow  to  very  nearly  dry,  and  iron  flat. 

The  fabric  must  be  well  sized  to  keep  the  image  on 
the  surface.  Arrowroot  is  one  of  the  best  sizes. 
Immerse  the  fabric  in  a  thin  gelatinous  solution  of 
arrowroot  for  a  few  minutes,  pin  down  to  a  board, 
and  dry  before  the  fire.  The  fabric  should  be 
slightly  stiff  after  drying.  An  arrowroot  and 
gelatine  size  is  recommended  by  E.   A.   Robins.  * 


Arrowroot, 

50  grains. 

10  grams. 

Nelson's  gelatine, 

•     18      „ 

3      „ 

Alum, 

.     11      „ 

2 

Water, 

12  ounces. 

1000  c.cs. 

The  Photogram,  1897  (June),  p.  171. 


54  FERRIC  A$T>  HELIOGRAPHIC  PROCESSES 

The  sensitising  solution  (ferro-prussiate,  Kallitype, 
etc. )  is  brushed  over,  and  the  fabric  dried  as  quickly 
as  possible.  For  effective  prints  the  negative  should 
be  broad  in  subject,  of  vigorous  density,  and  without 
a  superabundance  of  detail.  Often  negatives  which 
have  been  discarded  as  too  hard  for  paper  printing 
will  be  found  to  possess  the  characteristics  requisite 
for  decorative  work  on  fabrics.  If  they  are  to  be 
made  specially,  photo-mechanical  or  lantern  plates 
should  be  used  and  development  adjusted  to  get 
contrasty  negatives. 

Ferro-prussiate  prints  on  fabrics  will  not  withstand 
washing  in  soap  and  water,  as  the  free  alkali  destroys 
the  blue  image.  A  process  for  replacing  the  blue 
image  by  various  adjective  dyes  has  been  developed 
by  Stewart  E.  Carter.  * 

Bleached  cotton  or  linen  fabric  is  brushed  over 
with  a  ferro-prussiate  sensitiser  made  as  follows  : — 

Ferric  am.  citrate,      .     164  grains.       375  grams. 
Water,       ...         1  ounce.      1000  c.cs. 

Potass  ferricyanide,    .     164  grains.       375  grams. 
Water,       ...         1  ounce.      1000  c.cs. 

Use  equal  parts.  Expose  and  wash  as  usual.  The 
blue  print  is  next  immersed  in  a  weak  solution  of 
caustic  soda. 


Caustic    soda   sol.    (sp.  I 
gr.  1-35),  .         .           f 

1-2  mins. 

2-5  c.cs. 

Water, 

10  ounces. 

1000    „ 

*  Journ.  Soc.  Chem.  Indus.,  1898  (May),  p.  436,  and  British 
JouttwZ  of  Photography,  July  7,  1898. 


PRINTS  ON  FABRICS  55 

The  strength  of  this  solution  is  approximately — 

Caustic  soda,     .         .       5  grains.  1*1  grams. 

Water,       .         .         .10  ounces.       1000  c.cs. 

It  is  next  well  washed  in  hot  water  and  placed  in — 

Sodium  hyd.  phosphate,     13  grains.  3  grams. 

Water,      .         .         .         10  ounces.  1000  c.cs. 

for  three  minutes  at  a  temperature  of  170°  Fahr. 
This  is  followed  by  washing  first  in  cold  and  then  in 
hot  (160°  Fahr.)  water,  after  which  the  print  is 
ready  to  receive  the  dye. 

A  weak  gelatine  solution  is  made  : — 

Glue  size,.  .         .     24  mins.  5  c.cs. 

Water,      .         .         .10  ounces.       1000    „ 

This  is  heated  to  160°  Fahr.  and  the  prints  moved 
about  in  it  for  two  or  three  minutes  ;  from  three  to 
five  grams  per  litre  (1  *3  to  2  *2  grains  per  ounce)  of 
dinitroresorcine  (resorcine  green)  is  added,  and  the 
temperature  raised  to  180°  Fahr.  As  soon  as  the 
shade  is  considered  full  enough  for  a  strong  picture, 
remove  to  boiling  water,  to  wash  out  all  unfixed  dye. 
The  whites  are  next  cleared  in  a  bath  of  neutral 
soap  (used  at  160°  Fahr. )  and  the  print  again  washed 
in  hot  water  and  finally  in  cold.  Other  dyes  besides 
resorcine  green  can  be  used.  Gallocyanine  gives 
violet  and  blue ;  alizarin  gives  purple  ;  alizarin 
brown,  sepia.  A  somewhat  similar  process  has  been 
patented  by  A.  ,F.  Hargreaves  (Eng.  Patent,  25,043, 
1898).  The  blue  iron  compound  is  said  to  behave 
like  oxide  of  iron  as  a  mordant.     The  blue  prints 


56  FERRIC   AND   HELIOGRAPHIC   PROCESSES 

are  therefore  subjected  to  the  action  of  a  dye  bath 
containing  madder,  alizarin,  purpuric,  or  logwood. 
The  bath  is  first  used  at  100°  Fahr. ,  and  is  raised 
during  thirty  to  forty  minutes,  to  boiling,  then 
agitated  the  whole  time.  The  prints  are  then  well 
washed,  treated  to  a  boiling  solution  of  soap,  again 
washed,  dried  and  pressed. 


CHAPTEE    IX 

HELIOGRAPHIC   PROCESSES   COMPARED 

Some  idea  of  the  use  made  of  heliographic  copies 
of  tracings  by  engineers,  architects,  surveyors  and 
others  may  be  gathered  from  the  estimate  of  the 
Wm,  Cramp  &  Sons  Ship  and  Engine  Building  Co. , 
that  11,000  square  feet  of  blue  paper  are  used  in 
the  building  of  a  battleship. 

"Who  introduced  the  iron  copying  processes  to 
engineers,  the  writer  does  not  know.  In  America 
Thomas  H.  ATCollin  has  been  credited  with  doing 
so  in  1871.* 

"  It  should  be  noticed  that  the  terms  positive  and 
negative,  as  applied  to  these  processess,  are  held  by 
engineers  to  have  meanings  as  follows  : — A  '  positive  ' 
paper  is  one  which  gives,  for  an  ordinary  line  tracing, 
a  copy  in  dark  lines  on  a  white  ground  ;  a  '  negative  ' 

*  American  Journal  of  Photography,  1894,  p.  481  (Nov.). 


HELlOGRAPHiC  PROCESSES  COMPARED  57 

paper  is  one  which  gives,  under  similar  circumstances, 
a  copy  in  white  lines  on  a  dark  ground. 

For  large  work  the  chief  processes  are  four  in 
number  : — 

Process.  Copy  from  line  tracing. 

Ferro-prussiate.  White  lines  on  blue  ground. 

Pellet.  Blue         „      „  white      ,, 

Ferro-gallic.  Black       „      ,,       „         ,, 

Brown.  White      ,,      .,  brown     ,, 

Ferro-prussiate,  is  the  simplest  and  cheapest  of 
these.  It  requires  only  the  sligthest  experience  to 
work  it  successfully,  and  necessitates  the  smallest 
outlay  in  the  way  of  baths  and  space.  Formerly 
its  slowness  in  printing  was  one  of  its  chief  dis- 
advantages, but  paper  is  now  obtainable  which 
almost  rivals  '  Pellet '  paper  in  rapidity.  Its  blue 
ground  is  the  chief  objection  which  draughtsmen 
urge  against  it,  though  the  writer  has  often  heard 
mechanics  and  others  (who  use  blue  prints  in  the 
shops)  say  that  they  prefer  them  to  the  white  ground 
copies. 

'  Pellet  '  paper  is  known  by  various  other  names, 
such  as  '  Cyanof er, '  '  Positive  Ferrotype, '  '  Cyano- 
graphic, '  etc.  It  is  certainly  the  most  rapid  paper, 
and  for  winter  work  especially  valuable.  It  requires 
greater  skill  and  experience  to  work  it,  and  a  series 
(four)  of  baths  for  development  and  subsequent 
treatment. 

Ferro-gallic  paper  is  much  less  sensitive  than 
'  Pellet, '  but  scores  over  the  latter  in  its  simplicity 
of  after-treatment,  requiring  only  one  chemical  bath, 


58  FERRIC   AND   HELIOGRAPHIC   PROCESSES 

or,  in  the  case  of  the  '  water-developing  '  paper, 
merely  washing  in  water.  The  black  line  is  said  to 
be  preferred  to  the  bine  of  the  Pellet  paper  as  giving 
a  more  truthful  copy  of  the  tracing,  a  preference 
which  is  purely  a  matter  of  taste  and  should  be  put 
alongside  the  fact  that  the  ferro-gallic  process  rarely 
gives  the  absolutely  white  ground  which  '  Pellet ' 
paper  does,  a  faint  violet  tinge  being  almost  always 
unavoidable. 

The  '  brown  '  or  '  sepia  '  is  a  process  which  is  com- 
ing into  favour  on  account  of  its  rapidity,  simplicity, 
and  particularly,  because  of  its  adaptability  to  turning 
out  a  number  of  positive  copies  (brown  line  on  white 
ground)  from  a  negative  intermediate  (white  line  on 
brown  ground),  printed  directly  from  the  tracing 
(page  102). 

Other  processes  which  are  used  to  a  much  smaller 
extent,  and  chiefly  for  fine  work,  are  described  in 
Chapter  XVII.  Platinotype  (which  is  not  there 
described)  is  also  used,  and  gives  very  perfect  copies. 
Unfortunately  its  expense  and  the  precautions  needed 
in  its  use  preclude  its  general  adoption,  though  it  has 
been  used  to  a  fair  extent  for  the  reproduction  of 
reduced  copies  of  drawings.  The  Locomotive  De- 
partment of  the  L.  &  N.-W.  Railway  Co.  is  a  case 
in  point. 

-  Which  of  these  processes  shall  be  adopted  by  a 
drawing  office  setting  up  a  heliographic  outfit  is  a 
question  upon  which  it  is  not  easy  to  give  advice. 
For  occasional  prints,  such  as  an  architect  or  sur- 
veyor is  likely  to  require,  the  ferro-prussiate  or 
ferro-o-allic  is  best  suited.     Por  the  regular  routine 


PREPARATION   OF   HELIOGRAPRTC   PAPERS  59 

of  a  factory,  where  a  large  number  of  prints  are 
wanted  every  day  and  often  urgently,  the  '  Pellet ' 
process  should  certainly  be  installed.  At  any  rate, 
the  foregoing  few  hints  will  help  the  reader  to  decide 
for  himself. 


CHAPTEE   X 

Preparation  of  Heliographic  Papers 

Ferro-prussiate — Pellet — Ferro-gallic — Brown-line 

Ferro-prussiate. — Although  few  printing  houses 
will  wish  to  themselves  prepare  Pellet  and  ferro- 
gallic  papers,  the  coating  of  ferro-prussiate  paper 
demands  so  much  less  skill  than  either  of  these 
processes  that  many  printers  may  very  well  prepare 
it  for  their  own  use.  Apart  from  the  question  of 
diminished  cost,  the  superior  results,  consequent  on 
the  employment  of  fresh  paper,  will  make  the  pro- 
cedure worth  while. 

For  a  satisfactory  and  rapid  printing  paper  the 
writer  recommends  the  formula  given  on  page  14, 
which  is  here  repeated  : — 

Ferric  am.  citrate  (green),    110  grains.       250  grams. 
Water,    ....        1  ounce.      1000  c.cs. 

Potass  ferricyanide,  .      40  grains.         90  grams. 

Water,     ....        1  ounce.      1000  c.cs. 


>     1  ounce.    113  grains.     260  grams. 


60  FERRIC   AND   HELIOGRAPHIC   PROCESSES 

Mix  equal  volumes.  This  keeps  well  in  the  dark, 
beyond  requiring  to  be  filtered  just  before  use,  and 
prints  very  rapidly. 

An  equally  good  though  slower  formula  is  : — 

A.  Ferric    am. 

citrate, 
Water,  .       4£  ounces      1  ounce.   1000  c.cs. 

B.  Potass  ferri- 1      _  __        .         ^nn 

}     5  ounces.     75  grams.    172  grams, 
cyanide,     J 

Water,  .     32       ,,  1  ounce.   1000  c.cs. 

Mix  equal  parts  (Lietze). 

A  standard  formula  is  that  of  Fisch.  * 

Tartaric  acid,         .     3  ounces.    153  grains.         95  grams. 
Water,  .         .         .   13      „  90  mins.        375  c.cs. 


Ferric  chloride  sol. 

(sp.  gr.  1-45), 
Liq.     ammonia 

(•880),  not  more  V  6      „  70     „  175 


390     „  80 


than 

Potass     (  2  ounces 

ferri-       <  (av.),      — 2      „  360  grains.  70-80  grams, 

cyanide,  (  205  grs. 
Water,  .         .         .     9      „  325  min.  270  c.cs. 

Dissolve  the  tartaric  acid  in  the  water,  add  the 
iron  solution,  and  then  the  ammonia,  with  constant 
shaking  till  neutral.  Add  now  the  ferricyanide 
solution  with  constant  shaking,  cool,  and  keep  in 
well-corked  bottles  in  the  dark. 

It  would  be  easy  to  multiply  formula?,  but  one  or 
two  from  authoritative  sources  may  be  given. 

*  La  Photocopie,  p.  32,  Paris,  1890. 


PREPARATION   OF   HELIOGRAPHIC    PAPERS  61 

C.  B.  Talbot  *  gives  :— 


Potass  ferricyanide, 

53  grains. 

122  grams. 

Liq.  ammonia  ("880),    . 

4  mins. 

8  c.cs. 

Ferric  am.  citrate, 

86  grains. 

197  grams. 

Distilled  water,    . 

1  ounce. 

1000  c.cs. 

Dissolve  the  ferricyanide  in  the  water,  let  stand  a 
few  hours,  add  the  ammonia  and  then  the  dry  flakes 
of  ferric  am.  citrate,  stirring  these  in  with  a  glass 
rod.  One  fluid  ounce  coats  1|  square  yards  of  paper  ; 
100  c.cs.  coat  4|  square  metres. 

Another  very  sensitive  sensitiser  is  : — 

Ferric  chloride  (cryst.),  175  grains.  400  grams. 

Oxalic  acid,           .         .  44      „  100      „ 

Water,         ...  1  ounce.  1000  c.cs. 

Potass  ferricyanide,      .  88  grains.  200  grams. 

Water,         ...  1  ounce.  1000  c.cs. 

Mix  the  two  solutions.  The  coated  paper  keeps 
only  a  very  short  time. 

The  rolls  of  paper  are  sensitised  on  a  table  about 
half  an  inch  narrower  than  the  width  of  the  roll. 

A  roller  at  one  end  of  the  table  delivers  the  paper 
as  required,  and  a  drying  frame  at  the  other  end 
serves  to  receive  the  coated  paper  in  serpentine  folds 
for  drying.  The  top  of  the  drying  frame  is  provided 
with  six  or  eight  detachable  rods,  which  are  slipped 
underneath  the  paper  as  each  table-length  comes  from 
the  coater's  hands,  and  placed  in  slots  provided  for 
them  in  the  frame  (fig.  1).  By  enclosing  the  drying 
frame  in  a  closet,  in  the  lower  part  of  which  a  coil  of 

*  The  International  Annual,  1889-90,  p.  233,  Anthony  &  Co., 
New  York, 


62 


FERRIC   AND   HELIOGRAPHIC   PROCESSES 


steam  or  hot-water  pipes  is  fixed,  the  paper  is  quickly- 
dried  (C.  B.  Talbot). 

Coating  should  be  done  with  a  fine  sponge,  taking 
off  any  surplus  sensitiser  with  a  second  sponge,  only 
just  moist  with  sensitiser.  The  dry  coated  paper 
should  be  of  a  greenish-yellow  color,  and  must  be 
kept  as  dry  as  possible  in  a  moderately  warm  place. 
Damp  is  fatal  to  its  keeping  properties. 


Fig.  1. — Coating  and  Drying  Paper. 

For  coating  by  machinery  two  types  of  machine 
are  used.  The  following  account  of  their  construc- 
tion is  from  a  paper  by  Alfred  L.  Cohn  *  :  — 

' '  In  fig.  2  is  shown  a  machine  used  chiefly  on  the 
Continent.  In  this  the  framework  is  of  iron.  The 
roll  of  paper,  a,  to  be  sensitised,  is  placed  on  its 
bearings,  and  the  paper  led  over  an  arc-shaped  sheet 
of.  zinc,  b,  to  afford  the  necessary  friction  and  keep 
the  paper  smooth ;  it  then  passes  under  the  roller 
c  and  over  d.  From  this  the  paper  is  taken  up  and 
carried  over  an  endless  felt  belt,  stretched  over  the 
rollers  e  and  t,  whence  it  passes  through  a  narrow 

*  Journal  Soc.  Chem.  Indus.,  1902,  p.  582. 


PREPARATION   OF   HELIOGRAPHIC    PAPERS 


63 


slit  into  a  long  closed  chamber  10  to  20  feet  in 
length,  wherein  it  is  dried,  and  on  its  issuing  is  led 
back  to  the  machine,  where  it  is  wound  up  on  the 
roller  g.  The  bottom  of  the  drying  chamber  is  made 
of  sheet  iron,  and  is  heated  by  Bun  sen  burners,  or 
coils  of  steam  pipe  are  laid  inside  the  chamber. 
The  vapour-charged  air  within  the  chamber  is  removed 
by  means  of  an  exhaust  fan  or  blower. 


Fig.  2. 

a,  roll  of  paper  ;  b,  guide  to  sensitising  rollers  c  and  h  ;  d,  guide 
roller  (sensitised  paper) ;  g,  collecting  roller.  Glass  scraper 
between  c  and  d. 

' '  The  paper,  whilst  passing  around  the  roller  c, 
becomes  charged  with  the  sensitising  solution  which 
is  applied  by  the  roller  h.  This  roller  is  made  to 
revolve  towards  the  paper,  and  dips  into  the  sensi- 
tising solution  contained  in  the  trough  i.  At  a 
convenient  place  between  the  rollers  c  and  d  is 
fastened  the  scraper,  a  sheet  of  glass,  one  edge  of 
which  is  bevelled,  and  which  is  held  in  a  frame 
pivoted  to   the  iron   frame   of   the   machine.     The 


64 


FERRIC   AND   HELIOGRAPHIC   PROCESSES 


scraper  may  be  applied  against  the  paper  with  more 
or  less  pressure,  and  at  the  angle  best  suited  for 
securing  the  best  results.  In  some  machines,  wheels, 
h,  with  rubber  tyres,  are  placed  at  each  end  of  the 
roller  d,  and  are  operated  so  as  to  draw  the  paper 
along  at  its  edges  until  it  has  been  taken  up  by  the 
roller  g,  when  the  wheels  are  lifted  from  the  paper. 
Of  course,  the  paper  will  show  where  these  wheels 
passed  over  it. 

"The  machine  shown  in  fig.   3  is  constructed  of 


Fig.  3. 

c,  sensitising  roller  ;  d,  glass  scraper  ;  e  and  t,  guide  rollers  ; 
g,  collecting  roller. 

wood.  The  writer  has  operated  both  kinds  of 
machines,  and  prefers  the  latter,  which  he  considers 
much  the  better  of  the  two.  In  this  machine  the 
roll  of  paper  is  borne  by  a  carrier  sliding  in  grooves 
or  on  rails.  The  paper  is  first  passed  under  a 
tension  roller,  is  then  sensitised  by  the  roller  c,  the 
excess  of  liquid  being  scraped  off  by  the  glass 
scraper  placed  at  d ;  it  next  passes  over  the  rollers 
e  and  t  to  the  end  of  the  machine  (which  may  be  20 
or  30  feet  long,  or  any  convenient  length),  where  it 


FromH  Engineering "  May  5  1899. 


PREPAKATION   OF   HELIOGRAPHIC   PAPERS  65 

passes  over  two  rollers  and  returns  to  be  wound  up 
on  the  roller  g.  The  paper  in  its  passage  through 
the  length  of  the  machine  is  supported  by  a  criss-cross 
of  string  stretched  from  side  to  side,  in  order  to 
prevent  too  much  sagging,  and  yet  allow  the  paper 
to  be  thoroughly  dried  by  the  coil  of  steam  pipes 
placed  beneath  it. 

"  The  rolls  of  paper  as  ordinarily  received  are  of 
varying  widths,  30,  36,  42,  48,  etc. ,  inches,  and  contain 
usually  several  hundred  yards.  The  paper  is  wound 
on  a  wooden  cylinder,  with  a  hole,  either  square  or 
round,  running  lengthwise  through  it.  The  roll  of 
paper  is  supported  in  its  carrier  by  thrusting  through 
the  hole  in  the  wooden  cylinder  a  long  iron  rod  each 
end  of  which  is  threaded,  but  in  contrary  directions. 

' '  After  the  rod  is  in  place  a  tapering  nut  with 

hexagonal  or  octagonal  head,  fig.  4,  is  screwed  down 

on  each  end.     The  conical  parts  of 

the  nuts  enter  the  holes  in  the  ends 

of    the   wooden    cylinder,    and    on 

being  screwed  up  tight  the  roll  is 

centred  and  held  firmly.     The  rod 

bearing   the  roll   is   now  placed  in 

the  bearings   of   the   carrier.     The 

rod   is   threaded   oppositely  at  the  fig.  4.  _  Centring 

ends,  because  otherwise  one  of  the        ^  of  Delivery 

-,  -,    •  -tit  t  Roller  a. 

nuts  would  invariably  become  loose 

by  revolving  in  the  direction  in  which  the   paper 

is  pulled.     As  it  is,   it  is  safest  to  always  use  an 

additional   ordinary   nut,    which   is   screwed    down 

on  each  conical  nut  when  the  latter  has  been  firmly 

fixed  in  place. 


66  FERRIC   AND    HELIOGRAPHIC   PROCESSES 

' '  The  sensitising  liquid  is  contained  in  a  trough 
h,     which    is    preferably    made    of    hard    rubber. 
Galvanised   zinc,    however,    if   coated    with   shellac 
first   and,   when   dried,   with   an   asphalt   solution, 
answers  also.     The  sensitising  roller  may  be  either 
of  hard  rubber  or  wood  covered  with  felt  or  canton 
flannel.     The  scraper  may  be  a  sheet  of  glass  about 
3  or  4  inches  wide,  and  as  long  as  the  width  of  the 
machine.      It  is  well  to  have  both   the   long  edges 
cut  accurately  straight  and  rounded,  and  free  from 
nicks.     This  is,  however,  a  point  difficult  to  attain, 
hence  the   author   has   made   use   of   glass   tubing, 
which  may  be  had  perfectly  straight  and  round  ;  this 
gives  the  best  results.     The  sheets  of  glass  may  be 
supported  in  a  frame  of  wood  in  which  it  may  be 
easily  held   perfectly  tight,    yet   which   allows   the 
excess   of   liquid   scraped   off    the   paper   to   freely 
trickle  down  into  the  trough.     If  the  glass  tubing 
is   used,   it   should  be  cemented  into   a   frame  one 
edge  of  which  has  been  hollowed  out  to  receive  it. 
' '  When  very  or   even  moderately  thin  paper   is 
sensitised,    the   moistening   of   the   paper  allows   it 
to   stretch    considerably,   and  the  stretching   occurs 
most  at  the  middle  of  the  paper.     The  result  of  the 
stretching  is  to  cause  a  crinkling  of  the  paper  as  it 
passes   over   the   rollers  e   and   t,   and   longitudinal 
creases  form  which  totally  spoil  the  paper.     This  is 
obviated  by  replacing  e  and  t  by  rollers  which  are 
not  cylindrical,  but  which  are  thicker  in  the  middle 
than  at  the  ends  ;  and  the  thinner  the  paper,   the 
thicker  must  the  rolls  be  in  the  middle  as  compared 
with  the  ends. 


PREPARATION  OF  HELIOGEAPHIC  PAPERS     67 

' '  The  paper  is  started  on  the  machine  by  first 
winding  a  couple  of  hundred  yards  of  heavy  manilla 
paper  on  the  roll  g,  and  then  carrying  the  end  of 
this  paper  through  the  length  of  the  machine  and 
back  again  to  about  the  place  shown  at  k.  Here 
the  paper  drawn  from  the  roller  a  meets  it,  and 
the  two  are  pasted  together.  The  paper  is  then  run 
back  until  it  is  but  a  few  inches  in  front  of  the 
sensitising  roller. 

"  Power  is  supplied  at  g,  and  a  speed  of  about  100 
yards  per  hour  is  given  to  the  paper.  The  power 
must  be  steady  and  even,  and  must  absolutely 
impart  no  vibration  to  the  machine,  otherwise  a 
series  of  transverse  parallel  lines  will  become  visible 
on  the  paper  when  dry — due  to  the  fact  that  the 
liquid  remained  in  contact  for  a  fraction  of  a  second 
longer  on  one  spot  of  the  paper  than  it  did  on 
another,  and  the  liquid  will  have  soaked  into  the 
paper  so  much  the  more  the  longer  the  contact. 
The  utmost  care  must  be  observed  that  no  solid 
particles  of  matter  settle  in  the  angle  formed  by 
the  scraper  and  the  paper,  for  when  this  happens, 
the  paper  is  partially  lifted  from  the  scraper,  and  a 
long  longitudinal  streak  caused  by  an  excess  of 
sensitising  liquid  will  result. 

' '  The  form  of  machine  last  described  has  the 
advantage  that  the  top  may  be  used  as  a  table. 
The  sides  may  be  screened  with  oilcloth  or  other 
material,  thus  rendering  every  part  of  the  machine 
and  paper  easily  accessible,  which  is  very  important, 
as  sometimes  the  paper  does  not  run  perfectly  true, 
because  of  faulty  winding  up  on  its  spool,  stretching 


68 


FERRIC    AND    HELIOGRAPHIC   PROCESSES 


more  on  one  side  than  on  the  other,  faulty  alignment, 
etc.  Furthermore,  the  operator  has  always  before  him 
the  freshly  sensitised  paper  as  it  leaves  the  scraper, 
and  by  reason  of  the  arrangement,  is  enabled  to 
watch  over  the  details,  by  a  close  study  of  which 
alone  is  the  sensitising  of  paper,  even  with  a  well 
constructed  machine,  rendered  perfectly  successful. 
It  need  scarcely  be  mentioned,  of  course,  that  all 
movable  parts  of  the  machine  must  run  easily  and 
freely  and  without  a  jar,  and  all  the  bearings  be  kept 
well  oiled  and  free  from  dirt." 

Pellet  (blue   line  on  white  ground). 

This  process  is  perhaps  best  known  by  the  name 
of  Pellet,  who  brought  it  to  perfection,  though 
Pellet's  formula  is  a  trade  secret. 

The  paper  is  made  as  follows  (for  development, 
etc.,  see  page  94)  : — 

A  formula  for  coating  due  to  Pizzighelli  is  one 
winch  the  writer  can  recommend. 

Three  stock  solutions  are  required  : — 


A.  Pure  gum  arabic, 
"Water, 


88  grains.       200  grams. 
1  ounce.      1000  c.cs. 


B.  Ferric  am.  citrate, 
Water, 


220  grains.       500  grams. 
1  ounce.      1000  c.cs. 


C.  Ferric  chloride  (cryst.),  220  grains.       500  grams. 
Water,       ...       1  ounce.      1000  c.cs. 


The  gum  solution  keeps  only  a  few  days,  the  other 
two  for  many  weeks,  if  kept  well  corked  in  the 
dark. 


PREPARATION   OP   HELIOGRAPHIC   PAPERS  69 

To  make  the  sensitiser  take  : — 

Sol.  A.  (gum),     .         .         .20  vols. 
Sol.  B.  (citrate),  .  8    „ 

Sol.  C.  (chloride),        .         .       5    „ 

Add  B  and  C  to  A,  little  by  little,  shaking  between 
each  dose.  C  must  be  added  after  B.  Eeversal  of 
the  order  is  liable  to  cause  coagulation  of  the  gum. 
The  mixture  is  thick  at  first,  but  becomes  thinner 
after  a  few  hours.  It  keeps  in  good  condition  for 
two  or  three  days. 

Fisch*  gives  another  formula  : — 

Gum  arabic  (Senegal),     128  grains.       175  grams. 
Water,       ...         1  ounce.        600  c.cs. 

When  completely  dissolved,  filter  through  muslin, 
and  take  the  specific  gravity.  It  should  be  about 
1"090.  If  more  than  this,  add  water  little  by  little, 
shaking  well,  and  testing  with  the  hydrometer. 
The  solution  only  keeps  a  few  days. 

Tartaric  acid,     .         .175  grains.         40  grams. 
Water,       ...         1  ounce.        100  c.cs. 

This  ought  to  have  a  specific  gravity  of  1  "075  ;  if 
more,  add  water  as  above. 

Ferric  chloride  sol.  (sp.  gr.  T45). 

To  compound  the  sensitiser  take  : — 

Gum  solution,     20  ounces.     1000  c.cs. 

Add  little  by  little,  shaking  well : — 

Tartaric  acid  solution,     1  ounce  6-|  drams.     90  c.cs. 

*  La  Photocopie,  p.  15. 


70  FERRIC   AND   HELIOGRAPHIC   PROCESSES 

Well  mix,  and  add  slowly,  with  constant  shaking : — 

Ferric  chloride  )  2  ounces,  3  drams-2  ounces,  5  drams, 
solution,  J       120-130  c.cs. 

Test  the  mixture  with  the  hydrometer.  The 
gravity  should  be  1  '080  :  add  water  (well  mixing) 
until  it  registers  this  figure  within  a  division  or  two. 

The  paper  for  the  Pellet  process  must  be  well 
sized  and  calendered  to  resist  the  penetration  of  the 
sensitiser  into  the  fibre.  This  is  necessary,  to  avoid 
blue  staining  of  the  ground.  Special  papers  are 
sold  by  Steinbach,  Blanchet  Freres  and  Kleber, 
and  other  makers. 

Coating  is  by  brushing  or  floating.  For  the 
former,  spread  the  sensitiser  as  evenly  as  possible 
with  a  large  badger  brush,  working  the  brush  first 
lengthways  and  then  crossways  very  lightly,  to  get 
a  uniform  coat.  The  happy  medium  between  a  too 
thin  and  too  thick  coating  is  what  is  wanted.  The 
former  gives  prints  of  poor  vigour,  the  latter 
requires  a  longer  exposure  to  obtain  a  pure  ground. 

To  coat  by  floating,  Duchochois  directs  rolling  the 
paper  up,  sized  side  outwards,  and  placing  the  roll 
on  the  solution  contained  in  a  dish.  The  two  ends 
of  the  roll  are  slowly  drawn  out,  with  the  result  that 
the  paper  gradually  unrolls  itself  and  is  drawn  away 
coated  with  the  sensitiser.  It  is  dried  quickly  in 
the  dark,  and  keeps  for  a  long  time  preserved  from 
light  and  damp. 

Ferro-gallic. — For  development  with  gallic  acid 
(page  99),  paper  is  coated  with  a  mixture  containing 
ferric  chloride  and  tartaric  acid  with  gum  or  gelatine. 


PREPARATION   OF   HELIOGRAPHIC   PAPERS  71 

Colas,  to  whom  the  perfection  of  this  process  is  largely 
due,  gives  the  following  formula  *  : — 

Gelatine, 

Ferric  chloride  | 
(syrupy),         f 

Ferric  sulphate,    14 

Tartaric  acid, 

"Water, 

This  is  applied  in  the  same  manner  as  the  sensitising 
solution  in  the  Pellet  process. 

Lietze,  in  his  comprehensive  treatise  on  heliographic 
printing,  recommends  j-  the  following  : — 


14  grains. 

33 

grams. 

10 

grams. 

29      „ 

67 

jj 

20 

n 

14      „ 

33 

>j 

10 

•> 

14      „    ' 

33 

)! 

10 

>j 

1  ounce. 

1000 

CCS. 

300 

CCS. 

Gum  arabic, 

1 

ounce. 

67  grams 

Ferric  chloride  (solid), 

I 

)> 

50       „ 

Tartaric  acid,     . 

l 

2 

)5 

33       „ 

Monsell's  salt,  . 

1 

2 

J  J 

33       „ 

Water, 

15  ounces. 

1000  ccs. 

For  Monsell's  salt  see  page  21.  Development 
takes  place  in  gallic  acid  solution  (one  part  of  acid  in 
320  parts  of  water). 

Another  recent  formula  is  Nakahara's  I  : — 

Gum  arabic  .     59  grains.      135  grams.  15  grams. 

Tartaric  acid,        .       8      ,, 

Sod.  chloride  (salt),   36      ,, 

Ferric  chloride,     .59      „ 

Ferric  sulphate,    .     39      ,, 

Water,  .         .        1  ounce. 

*  Geiverblatt  aus  Wurtemberg,  1S86,  vol.  xxxiii. 
Handbuch,  1887,  vol.  iv.  p.  236. 

t  Modern  Heliographic  Processes,  Instruction  in  the  Art  of  Repro- 
ducing Drawings,  Engravings,  etc.,  by  the  Action  of  Light. 

%  Photo  Chronik,  1895,  p.  125;  The  Amateur  Photographer, 
March  29,  1895. 


18      „ 

2 

5) 

81      „ 

9 

)' 

135      „ 

15 

, 

90      „ 

10 

>> 

1000  ccs. 

110 

CCS. 

vol.  xxxiii. 

p.  365 

;  Eder's 

72  FERRIC   AND    HELIOGRAPHIC   PROCESSES 

Dissolve  the  guin  in  the  water  (hot)  and  add  the 
rest  of  the  chemicals  in  the  order  given.  Apply  the 
mixture  to  the  paper  with  a  sponge  ;  then,  squeezing 
out  the  sponge,  remove  as  much  as  possible. 

Ferro-gallic —  Water-bath.  — By  incorporating  gallic 
acid  or  other  developing  substance  with  the  salts  on 
the  paper  in  such  a  manner  that  no  reaction  takes 
place  between  the  iron  salts  and  the  gallic  acid,  a 
sensitive  paper  is  produced  which  gives  a  black-line 
copy  merely  by  washing  in  water  (page  100).  There 
are  two  methods  of  manufacture.  According  to  the 
older,  finely-powdered  gallic  or  tannic  acid  is  strewed 
over  the  paper  which  has  received  the  coating  of  iron 
salts.  According  to  the  more  recent  method,  the  coated 
paper  is  treated  with  a  solution  of  gallic  acid  con- 
taining also  a  substance  which  prevents  the  reaction 
between  ferric  salts  and  gallic  acid  until  (when  the 
copy  is  developed)  this  restraining  substance  is  largely 
diluted  with  water.  Hydrochloric,  oxalic,  and  tar- 
taric acids  act  in  this  way,  and  are  dissolved  along  with 
the  gallic  acid  in  a  solvent  which  can  be  applied  to 
the  paper  without  disturbing  the  coating  of  ferric  salt. 

A  formula  for  the  first  method  is  that  of  Shawcross 
and  Thompson,  who  took  out  a  patent  in  1884 
(English  patent,  No.  8771) : — 


Gelatine, 

60 

grains. 

1,500  grams. 

Ferric  sulphate, 

24 

>j 

600     „ 

Salt, 

37 

)> 

940     „ 

Tartaric  acid, 

7 

)> 

188     „ 

Ferric  chloride, 

60 

» 

1,500     „ 

Water,  . 

1 

ounce. 

11,000  c.cs. 

Finely -powdered  gallic  acid  is  dusted  over  the  paper, 


PREPARATION   OF   HELIOGRAPHIC   PAPERS  73 

which  has  received  a  coating  of  the  above  solution 
and  has  been  dried. 

Paper  to  be  treated  by  the  second  method  is  given 
a  coating  of  a  somewhat  similar  solution  to  the  above, 
and  after  drying  is  floated  on — 

Gallic  acid,      .     66-88  grains.     150-200  grams. 
Tartaric  acid,  .     22-35      „  50-80      „ 

Alcohol,  .  1  ounce.  1000  c.cs. 

Paper  prepared  by  this  process  develops — so  it 
is  stated  by  Messrs  Schering,  who  are  the  makers  of 
the  paper — very  much  more  quickly  than  that  manu- 
factured by  the  powder  process,  owing  to  the  fine 
state  of  division  of  the  gallic  acid.  On  immersion  in 
water,  the  equilibrium  existing  between  this  sub- 
stance and  the  tartaric  or  other  acid  is  upset,  and 
the  former  reacts  at  once  with  the  ferric  salts  with 
which  it  finds  itself  in  contact. 

Paper  for  ferro-gallic  must  have  a  hard  surface  and 
be  well  sized  in  order  to  prevent  the  ground  from 
becoming  stained.  Hancke  (English  patent  15,673, 
1901)  coats  cheap  porous  paper  with  an  insoluble 
layer  of  resin,  or  insoluble  gelatine,  and  on  top  of 
this  a  soluble  layer  of  starch  or  dextrine,  his  object 
being  to  utilise  such  cheap  paper  for  the  process. 

Broivn  line,  or  Sepia,  is  a  silver-iron  process  analo- 
gous to  Kallitype.  The  formula  on  page  41  answers 
perfectly  for  the  preparation  of  papers  intended  for 
copies  from  tracings  on  the  large  scale.  The  following 
formula  has  been  patented  by  Arndt  and  Troost,  of 
Frankf ort-on-Main,  *  who  made  paper  in  1894  as 
Sepia  Blitz-Lichtpaus  papier.  See  also  p.  104. 
*  English  patent  No.  20,358,  29th  June  1895. 


74  FEERIC   AND   HELIOGEAPHIC   PROCESSES 

A  paper  must  be  used  which  contains  no  chlorine  ; 
that  made  from  pure  rag  is  most  suitable.  The 
presence  of  wood  pulp  is  very  objectionable. 

The  sensitising  solution  contains  : — 


Ferric  am.  citrate, 

.  35-44  grains. 

80-100  grams. 

Tartaric  acid, 

■       7-9      „ 

15-20      „ 

Gelatine,    . 

•       4-7      „ 

10-15      „ 

Silver  nitrate,     . 

.       5-9      „ 

12-20       „ 

Distilled  water,  . 

1  ounce. 

1000  c.cs. 

.  62  gr. 

4      „ 

.  7oz. 

200  c.cs. 

.  93  gr. 

6  grams. 

.  3|-  oz. 

100  c.cs. 

Paper  is  soaked  in  this  solution  and  dried  ;  it  keeps 
unchanged  for  several  months. 

A  later  formula  of  Dr  Laurens  is  *  : — 

A.  Ferric  am.  citrate  (green),  1  oz.  103  gr.  35  grams. 
Tartaric  acid, 
Water,  . 

B.  Gelatine, 
Water,  . 

C.  10  per  cent,  silver  nitrate  solution. 

A  and  B  are  mixed  at  103°  Fahr.  and  the  silver 
added  with  constant  stirring.  The  paper  is  coated 
with  the  lukewarm  mixture.  The  solutions  and  the 
paper  should  be  free  from  chlorides. 

Two  decompositions  probably  take  place  when  the 
paper  is  exposed  to  light.  Some  of  the  silver  nitrate 
forms  (in  combination  with  the  gelatine)  the  dark- 
colored  '  gelatinate  of  silver, '  whilst  the  second  and 
predominant  reaction  is  that  of  the  reduction  of  the 
ferric  to  ferrous  salt,  the  latter  precipitating  metallic 
silver  from  the  silver  nitrate. 

*  Photographischc  Wochenblatt,  1898,  p.  305. 


MAKING   TRACINGS   FOR   SUN-COPYING  75 


CHAPTEE    XI 

Making  Tracings  for  Sun-copying 

Tracings  for  reproduction  by  ferro-prussiate  and 
allied  processes  should  be  on  thin  bluish  tracing 
paper.  Tracing  cloth  scarcely  gives  such  good  copies 
and  does  not  take  the  draughtsman's  ink  so  well  as 
the  paper.  Whichever  is  used,  a  yellowish-colored 
tracing  is  to  be  particularly  avoided.  Many  manu- 
facturers of  printing  papers  supply  specially  suitable 
tracing  cloths  and  papers. 

Lines,  dimensions,  etc. ,  should,  wherever  possible, 
be  drawn  in  thick  Indian  ink,  and  it  is  always  well 
to  add  a  little  chrome  yellow  or  gamboge,  or  a  little 
of  one  or  other  of  the  various  preparations  sold  for 
rendering  the  ink  more  opaque  to  actinic  rays.  The 
test  of  a  good  tracing  for  sun -copying  is  to  hold  it  up 
to  a  strong  light  and  to  closely  examine  the  opacity 
of  the  lines. 

Lines  in  colored  inks  never  come  out  so  well  as 
those  in  Indian  ink,  unless  an  exceptional  thickness 
of  ink  be  used,  in  which  case  the  brilliancy  of  the 
color  is  impaired.  Prussian  blue  should  be  avoided 
or,  if  it  is  used,  must  be  thickened  with  an  opaque 
pigment  like  Chinese  white  or  flake  white.  Indigo 
gives  better  results  than  Prussian  blue,  though  un- 
fortunately, if  applied  fairly  thick  is  scarcely  distin- 


76  FERRIC   AND   HELIOGRAPHIC    PROCESSES 

guishable  from  black.  Vermilion  is  the  best  color 
for  red. 

Wherever  possible,  it  is  best  to  use  Indian  ink  lines 
in  different  styles  of  punctuation  in  place  of  colored 
inks. 

It  is  sometimes  desired  to  color  the  sectional 
portions  of  the  printed  copies.  This  offers  no  diffi- 
culty in  the  case  of  prints  by  the  Pellet  and  ferro- 
gallic  processes,  but  for  ferro-prussiate  prints  the 
sectional  portions  of  the  original  tracing  must  be 
covered  with  an  opaque  color  like  Chinese  white. 
In  the  printed  copy  these  portions  will  be  practically 
white,  and  they  can  then  be  colored  as  desired. 

To  make  a  tracing  which  can  be  used  as  a  negative 
for  ferro-prussiate  paper  (giving  blue  lines)  on  a  white 
ground,  the  method  of  M.  Cheysson*  is  to  be  re- 
commended. 

Make  the  tracing  in  lithographic  ink.  The  ink  is 
prepared  by  rubbing  the  solid  stick  on  the  bottom  of 
a  large  saucer.  When  enough  has  been  thus  ground 
up,  a  very  little  distilled  water  is  added  (tap  water  is 
not  suitable)  and  the  whole  mixed  with  the  finger. 
If  not  of  the  requisite  consistency,  add  a  little  more 
water  and  grind  up  with  the  ink  till  a  dense  and 
liquid  mixture  results,  which  is  used  on  the  drawing 
pen  exactly  like  Indian  ink. 

Let  the  tracing  dry  and  place  on  a  board  covered 
with  one  or  two  thicknesses  of  blotting-paper.  With 
a  soft  brush,  coat  the  whole  surface  of  the  tracing  with 
a  solution  of  aniline  brown  (a  strong  solution  of  the 

*  Manual  des  proceeds  de  reproduction  d'ecritures  et  de  dessins 
a  employer  dans  le  service  des  ponts  et  chaussdes,  Paris,  1880. 


OUTFIT   FOR   HELIOGRAPHIC    PRINTING  77 

dye  made  in  hot  water  and  allowed  to  cool).  Be 
careful  to  get  none  on  the  back.  As  soon  as  dry,  rub 
the  paper  over  with  a  tuft  of  cotton- wool  or  soft  rag 
moistened  with  turpentine  until  the  ink  lines  of  the 
drawing  are  dissolved  away.  Tins  leaves  the  design 
in  transparent  lines  on  a  dark  brown  ground,  and  the 
process  will  yield  positive  prints  (dark  lines  on  white 
ground)  when  printed  in  ferro-prussiate  or  brown- 
line  processes. 

Tracings  must  on  no  account  be  folded  or  creased  : 
all  such  marks  will  show  in  the  copy. 


CHAPTEE    XII 

Outfit  for  Heliographic  Printing 

The  apparatus  necessary  for  the  equipment  of  a 
printing  house  is  not  very  expensive,  and  comprises 
printing  frames,  baths  for  development  and  washing, 
drying  arrangements,  benches  for  trimming  and 
mounting  copies,  and  racks  for  keeping  tracings 
which  have  or  have  not  been  copied.  These,  and  a 
small  room  for  the  storage  of  sensitive  paper,  will 
meet  the  requirements  of  the  blue  printer. 

Printing  Frames. — For  daylight  work  the  printing- 
frame  consists  of  a  strong  shallow  frame  with  a  plate- 
glass  front,  on  which  the  tracing  and  sensitive  paper 


78  FERRIC   AND    HELIOGRAPHIC   PROCESSES 

are  laid.  These  are  backed  up  with  a  thick  pad  of  felt, 
preferably  covered  on  its  under  side  with  vulcanised 
rubber  sheet.  The  back  of  the  frame  is  made  in 
several  sections,  pressure  on  each  being  applied  by 
means  of  a  series  of  vertical,  spiral,  or  other  springs, 
held  in  place  by  upright  pegs  fixed  to  the  back  itself. 
These  springs  exert  downward  pressure  on  the  back 
of  the  frame  and  upward  on  the  cross-bars,  which 
are  hinged  to  one  side  of  the  frame  and  secured  by  a 
catch  to  the  opposite  side.  A  properly  constructed 
frame  is  a  sine  gud  non,  since  it  is  most  essential  that 
the  tracing  and  sensitive  paper  shall  be  pressed  into 
firm  and  uniform  contact.  Any  defect  in  this  respect 
means  blurred  lines  in  the  copy. 

A  cheaper  form  of  printing  frame  which  does  not 
involve  the  use  of  a  glass  front  is  described  by 
C.  B.  Talbot*  as  specially  suitable  for  field  or  other 
purposes  where  portability  is  a  consideration.  Two 
end  boards  (fig.  5)  having  an  arch-shaped  groove, 
secured  to  a  hinged  frame  at  the  back,  have  placed 
therein  the  ends  of  some  loosely-fitting  tongued  and 
grooved  boards,  the  surfaces  of  which  are  formed  to  the 
radius  of  the  curve  (3  or  4  feet).  Each  board  is  about 
3  inches  wide  and  supported  loosely  on  a  bridge  at  the 
middle  of  the  back  of  the  same  shape  as  the  grooves. 
About  one  third  of  the  width  of  the  frame  is  hinged. 
The  edge  of  the  tracing  is  slipped  through  any  crack 
in  the  tongue  and  grooves  corresponding  to  its  width. 
On  the  narrow  side,  the  boards  near  the  edge  are 
made  of  different  widths,  say,  2J,  3,  3|,  4  inches,  so 
that  one  edge  of  the  tracing  being  placed  in  a  given 
*  Anthony's  International  Annual,  1889-90,  p.  235. 


OUTFIT   FOR   HELIOGRAPHIC   PRINTING  79 

crack,  the  other  edge  is  pretty  certain  to  find  a 
suitable  hold  on  the  other  side  of  the  hinge.  The 
tracing,  with,  of  course,  the  paper  beneath  it,  is 
stretched  by  pushing  the  board  closely,  allowing  the 
tracing  to  slip  easily  though  firmly  through  the  cracks 
between  the  boards  until  the  desired  tension  is  given  ; 
then  bringing  the  hinge  down  and  locking  it  at  the 
back  to  the  frame. 

The  pneumatic  printing  frame  of  H.  Sack,  Dtissel- 
dorf-Eath,  in  which  pressure  is  applied  to  the  back  of 
the  sensitive  paper  by  an  inflated  air-cushion,  is  used 


Fig.  5. — Unglazed  Printing  Frame. 

more  on  the  Continent  than  in  England.     Messrs 
Bemrose  are  the  British  agents. 

Printing  by  Electric  Light. — The  arc  light  is  now 
used  extensively  for  printing,  and  under  many 
circumstances  is  superseding  daylight  altogether. 
This  is  not  surprising,  since  in  the  winter  months 
daylight  is  available,  for  practical  purposes,  only 
two  or  three  hours  in  the  middle  of  the  day,  and 
several  days  may  be  spent  before  a  ferro-prussiate 
print  can  be  obtained — if  the  paper  is  not  spoilt 
by  undue  exposure  to  the  damp  weather  in  the 
meantime.     For  reasons  of  economy  of  time,  labor 


80 


FERRIC    AND    HELIOGRAPHIC   PROCESSES 


and  material,  therefore,  artificial  light  is  far  superior 
to  daylight,  especially  in  towns  where  the  light  is 
robbed  of  a  large  part  of  its  actinic  power  by  the 
overhanging  haze.     The  artificial  light   installation 

likewise  economises  space 
arid  makes  it  easy  to  take 
off  copies  even  in  a  drawing 
office  without  appreciable 
inconvenience. 

The  outfit  consists  of  a 
cylinder  (made  in  halves) 
of  polished  rolled  plate 
glass.  The  tracing  with 
the  sensitising  paper  behind 
it,  is  wrapped  around  the 
outside  of  the  cylinder  by 
a  canvas  apron.  The  arc 
lamp  suspended  above  the 
centre  of  the  cylinder  is 
lowered,  automatically  or 
by  hand,  into  the  cylinder 
and  kept  moving  up  and 
down,  within  a  determin- 
able range  for  as  long  as  is 
necessary  for  exposure. 

Tracing  and  paper  are 
inserted  very  rapidly  into 
place.  They  are  rolled  up  together,  with  the  tracing 
on  the  inner  side  of  the  roll.  The  latter  is  then 
placed  between  the  apron  and  the  glass  and,  by 
withdrawing  the  hand,  unrolled  in  contact  with  the 
glass.     The  loose  end  of  apron  is  then  strapped  to 


Fig.  6. — Hall's  Lamp. 


&£^*1ArtErt7-  &CAC+T    Z-//V4T    F*Hc>-TO-F>/*/rrr  TAKE*  BY ELCCTRfC  LJC*n~ 

B.  J.  HALL  4  C'  39,  V/cfcrt'aSfeef;  (f?d>y  «S  Iff 


OUTFIT   FOR   HELIOGKAPHIC    PRINTING  81 

the  cylinder  and  contact  made  by  a  lever-tightening 
gear,  which  squeezes  tracing  and  paper  very  tightly 
and  smoothly  against  the  glass. 

The  lamp  descends  slowly  or  quickly,  according 
as  the  paper  is  rapid  or  slow,  this  range  of  speed 
being  necessary  to  equally  illuminate  the  tracing. 
In  B.  J.  Hall's  lamp  (fig.  6)  the  gear  regulating 
this  movement  is  very  simple,  and  in  the  lamps  as 
now  made  is  outside  the  supporting  pillar. 

In  addition  to  the  automatic  movement,  which  is 
actuated  by  the  lamp  itself,  there  is  a  hand  adjust- 
ment. 

The  following  times  are  given  by  Hall  for  fully 
exposed  copies  from  two  double-elephant  tracings  on 
clear  blue-slate  tracing  paper,  using  the  No.  1 
lamp  : — 

Very  slow  ferro-prussiate  paper  (blue  print)  8  minutes. 
Ordinary  ferro-prussiate  paper  „  3  „ 

Rapid  ferro-prussiate  paper  „  1£        „ 

Ferro-prussiate  linen  „  4  „ 

Black  line  water-bath  paper  ,,  7  to  8  „ 

Sepia  negative  from  tracing  3  „ 

Sepia  negative  from  inked  drawing  15  ,, 

Sepia  negative  on  Whatman's  paper  15  „ 

Sepia  positive  from  negative  8  ,, 

Sepia  positive  linen,  from  negative  12  „ 

Pellet  (blue  line  white  ground)  1J        ,, 

The  Hall  lamp  is  supplied  in  four  standard  sizes  : — 
No.  1  is  a  10-ampere  lamp,  taking  120  volts  across 
the  arc,  used  for  continuous  current  ;  No.  2  is  a  12- 
ampere  lamp,  taking  75  to  90  volts  across  the  arc, 

6 


Fig.  7.— Hall's  Lamp. 


OUTFIT   FOR   HELIOGRAPHIC    PRINTING  83 

used  for  continuous  current ;  No.  3  is  a  20 -ampere 
lamp  taking  75  to  90  volts  across  the  arc,  used  for 
continuous  current ;  No.  4  is  a  15-ampere  lamp, 
taking  75  to  90  volts  across  the  arc,  used  for 
alternating  currents. 

Taking  the  time  for  exposure  as .  unity  when  lamp 
No.  1  is  used,  No.  2  equals  1 -75,  No.  3  equals  1  "25, 
No.  4  equals  2.  The  alternating  lamp  is  thus  the 
least  satisfactory,  and  the  most  expensive  in  energy 
for  photographic  purposes. 

Halden's  lamp  can  be  turned  into  the  horizontal 
position  for  the  more  convenient  filling  and  emptying 
of  the  frame  ;  the  tracing  lies  on  the  glass  plate 
(when  the  frame  is  horizontal)  while  a  fresh  piece 
of  sensitive  paper  is  inserted. 

A  machine  (Spaulding's  patent)  is  said  to  be  used 
in  America  under  the  name  of  the  'Federal,'  as 
shown  in  fig.  8.  The  tracing  and  sensitive  paper 
are  fed  round  a  large  wooden  drum  around  which 
a  transparent  apron  is  tightly  drawn.  The  drum 
is  moved  by  connection  from  shafting  or  by  an 
electric  motor.  The  apron  is  wound  from  a  lower 
roller  to  an  upper  one,  and  back  by  hand.  Three 
arc  lights  concentrated  by  a  reflector  are  said  to 
expose  the  paper  as  it  passes  over  the  illuminated 
field. 

An  electric  lamp,  intended  for  projection  but  suit- 
able for  printing  in  small  sizes,  is  made  by  Grass  & 
Worff,  Berlin.  It  is  made  for  continuous  or 
alternating  current,   110  or  220  volts  (fig.   9). 

Very  long  tracings  are  not  easily  printed  in  the 
ordinary  frames.     The   suggestion   has   been   made 


84 


FERKIC   AND   HELIOGRAPHIC   PROCESSES 


by  Cleaves*  to  print  them  around  a  circular  drum 
having  a  slit  in  its  side  to  allow  of  access  to  two 
rollers  in  the  interior.  The  tracing  and  sensitive 
paper  are  wound  together  round  one  roller,  brought 
out  through   the  slit,   taken  round  the   drum,   and 


8. — Spaulding's  Rotary  Printer. 


stretched  tight  by  means  of  the  second  roller.  The 
drum  is  rotated  during  printing,  and  after  exposure 
a  second  length  of  tracing  and  paper  is  unwound  from 
the  first  roller  whilst  the  exposed  portion  is  coiled 
round  the  second. 

*  Memoir   by  Prof.    R.   H.  Thurston,  Washington   Meeting   of 
Mechanical  Engineers,  1887. 


OUTFIT   FOR   HELIOGRAPHIC    PRINTING  85 

Washing  and  Developing  Baths. — For  washing  iu 
plain  water,  the  most  satisfactory  material,  taking 
price  into  consideration,  is  zinc,  and  baths  of  this 
material  can  be  used  for  developing  ferro-prussiate 


Fig.  9.— Grass  &  WorfFs  Lamp. 

and  ferro-gallic  and  brown-line  prints,  and  for  the 
final  washing  of  copies  on  Pellet  paper.  They  must 
not  be  used  for  the  ferrocyanide  and  acid  bath 
required   in    the    Pellet    process,    for   which    iea(j_ 


86      FERRIC  AND  HELIOGRAPHIC  PROCESSES 

lined  wood  trays  or  papier-mache  are  necessary. 
Wooden  wax-coated  trays  are  readily  made  at  a 
small  cost,  and  can  be  used  for  practically  all  the 
blue  printers'  solutions.  Yellow  pine  is  the  best 
material,  being  dovetailed  together,  made  quite  hot 
before  a  fire,  and  melted  paraffin  wax  poured  in 
as  evenly  as  possible  :  any  irregularities  can  be 
corrected  with  a  hot  iron.  The  outsides  of  the  trays 
should  be  varnished  with  shellac  varnish.  Another 
suitable  protective  coating  for  the  inside  is  : — 

Brown  resin,  ....         4  parts. 
Bees-wax,        ....  1  part. 

These  are  melted  together  and  applied  hot. 

The  baths  should  be  of  ample  size  :  it  is  a  mistake 
to  stint  matters  in  this  respect.  .  A  safe  rule  is  to 
have  them  six  inches  larger  than  the  largest  tracing 
which  the  printing  frames  will  accommodate.  They 
are  arranged  on  trestles  with  a  water  tap  (with 
rubber  tube  attached)  at  one  end.  In  winter  an  oil 
or  gas  stove  or  coil  of  steam  pipes  is  required  under 
the  Pellet  developing  bath  and  others.  Each  bath 
should  be  kept  for  one  particular  purpose  and  no 
other.  Neglect  of  this  is  the  cause  of  much  trouble 
in  the  matter  of  stains. 

For  office  use,  where  space  is  limited,  B.  H. 
Thwaite*  prefers  to  use  a  vertical  washing  bath  for 
ferro'-prussiate  prints,  suspending  the  copy  in  the 
water  from  a  light  lath  laid  across  the  top  of  the 
bath  (fig.  10). 

Drying   Arrangements. — An   efficient    drying  ap- 

*  Proc.  Inst.  Civ.  Eng.,  1885-86,  Pt.  IV.  p.  812. 


OUTFIT   FOR   HELIOGRAPIIIU   PRINTING 


87 


paratus  is  described  and  illustrated  on  p.  61,  and 
a  small  room — or  a  corner  of  a  developing  house 
partitioned  off — fitted  up  with  a  similar  arrange- 
ment and  furnished  with  a  coil  of  steam  pipes  in  the 
base  and  an  outlet  for  air  above,  will  speedily  dry 
prints,  whatever  may  be  the  state  of  the  weather. 
Otherwise  a  series  of  drying  rods  or  lines  with  a  gas 
stove  fixed  close  at  hand  is  a  practical  though  less 


FIR.  10.— Vertical  Washing  Bath.     (B.  H.  Thwaite.) 

certain  method.  Tor  attaching  prints  to  the  drying- 
rods,  clips,  in  shape  of  an  inverted  f)>  are  used,  or 
photographers'  '  push-pins  '  are  very  convenient. 
For  attaching  to  lines,  the  usual  clips  are  employed 

(%•  ID- 

Other  Fixtures. — A  couple  of  solid  tables  for 
trimming  and  mounting  prints  are  necessary  items 
in  the  outfit,  as  are  also  some  racks  in  which  to  file 


88 


FERRIC   AND   HELIOGRAPHIC   PROCESSES 


tracings  which  await  printing  or  are  being  retained 
for  future  use. 

A  small  room  kept  warm  a  d  dry  should  be  set 
apart  for  the  storage  of  the  sensitive  papers,  the 
opened  rolls  of  which  should  be  stored,  when  not  in 
use,  in  light-tight  tin  cases. 

The  illumination  of  the  place  used  for  developing 
must  be  subdued.  Weak  daylight  is  very  generally 
used  with  satisfactory  results.     If  sunlight  has  to 


Fig.  11. — Drying  Clips  and  Pins. 

be  excluded  from  any  window,  yellow  tissue  paper 
pasted  on  the  glass  will  be  found  to  answer. 

The  arrangement  of  the  printing  house  will,  of 
course,  depend  very  largely  on  local  conditions  and 
requirements.  Where  spa.ce  and  an  open  view  are 
available,  a  yard  in  front  of  the  premises,  into  which 
the  printing  frames  can  be  wheeled,  is  convenient. 
In  towns  it  is  often  necessary  to  utilise  the  roof  of  a 
building  for  printing  purposes.  In  offices  to  which 
daylight  has  no  very  free  access,    the  exposure  is 


OUTFIT   FOR   HELIOGKAPHIC    PRINTING  89 

shortened  by  the  use  of  two  reflectors,  one  outside 
the  window,  face  upwards  at  an  angle  of  45°  to  the 
horizontal,  and  one  inside,  above  the  window  and 
face  down,  at  the  same  inclination.  The  light  from 
the  sky  is  reflected  from  the  first  mirror  to  the  second 
and  thence  to  the  printing  frame.  Sometimes  the 
latter  can  be  raised  to  the  roof  and  exposed  to 
the  direct  light  of  the  sky,  reaching  it  through  a 
fanlight. 

Water  Supply.  — The  quality  of  the  water  used  for 
washing  blue  prints  is  a  point  which  may  in  certain 
cases  require  attention.  It  is  pointed  out  on  page  145 
that  weak  alkalies — even  calcium  carbonate  in  solu- 
tion— decompose  Prussian  blue,  whence  it  follows 
that  the  '  softer  '  a  water  is  the  more  suitable  for  the 
purposes  of  the  blue  printer.  For  practical  purposes 
the  quantities  of  carbonate  of  lime  and  other  salts  in 
most  town  waters  have  no  appreciable  action  within 
the  limits  of  ordinary  manipulation.  Cases  do,  how- 
ever, arise  where  the  water  makes  itself  known  by  its 
weakening  action  on  the  blue  ground  or  line  of  the 
print.  An  instance  was  recently  brought  to  the 
writer's  notice  where  a  printing  house  was  being- 
supplied  with  water  containing  over  40  grains  of 
carbonate  of  soda  (expressed  as  ISTagCOg)  per  gallon, 
which  speedily  reduced  the  intensity  of  the  prints. 
The  application  of  a  chemical  test  (the  estimation  of 
the  alkalinity,  etc. )  will  at  once  tell  whether  a  water 
supply  is  unsuitable  in  this  respect. 


90  FERRIC   AND    HELIOGRAPHIC    PROCESSES 


CHAPTEE    XIII 

PERRO-PRUSSIATE,  OR  WHITE  LlNE  ON  BLUE  GROUND 

White  Line  on  Blue  Ground. — The  making  of  the 
sensitive  paper  has  been  described  on  pages  11  and 
59.  The  tracing  is  laid  face  down  on  the  glass  of 
the  printing  frame,  and  a  piece  of  sensitive  paper,  of 
such  size  as  to  project  about  two  inches  all  round, 
laid  upon  it.  The  felt  pad  and  the  back  of  the  frame 
having  been  fixed,  the  whole  is  exposed  to  light,  and 
the  progress  of  printing  judged  by  observing  the  out- 
side portion,  which  gradually  changes  from  yellowish- 
green  through  bluish-green  and  slaty-grey  to  olive- 
green,  the  tint  corresponding  to  correct  exposure 
differing  slightly  with  different  brands  of  paper.  A 
minute  or  two's  exposure  beyond  this  point  will  (in 
the  case  of  ordinary  tracing  paper  or  cloth)  leave  the 
print  properly  exposed.  Prints  from  thicker  and 
more  opaque  paper  must,  of  course,  receive  much 
longer  exposure,  and  it  is  generally  necessary  to 
examine  the  print  itself. 

Exposure  may  be  gauged  by  meter,  and  for  this 
purpose  a  very  convenient  instrument  is  Wynne's 
print  meter.  The  meter  (fig.  12)  consists  of  a  small 
metal  case  with  a  front  of  opal  and  a  hinged  back, 
carrying  inside  a  sensitive  paper.  Behind  the  opal 
face  is  a  plate,  perforated  with  a  series  of  diaphragms 


FERRO-PRUSSIATE,  OR  WHITE  LINE  ON  BLUE  GROUND    91 

which  serve  to  admit  different  intensities  of  light  to 
a  series  of  figures  on  a  glass  plate,  which,  when  the 
meter  is  closed,  is  pressed  into  contact  with  the 
sensitive  paper  on  the  back  of  the  instrument.  On 
exposing  the  meter  to  light,  the  light  gradually  im- 
presses the  graduated  scale — which  is  numbered  1  to 
16  and  then  onwards  A  to  P — on  the  sensitive  paper. 


Fig.  12.— Wynne's  Print  Meter. 

In  using  the  meter  for  timing  blue  prints,  a  pre- 
liminary test  exposure  is  made,  paper  and  meter  being 
exposed  simultaneously  to  the  same  light.  As  soon 
as  the  print  is  correctly  exposed,  the  last  number  (just 
readable)  registered  on  the  meter  is  noted,  and,  in  all 
future  work  with  the  same  brand  of  paper  and  quality 
of  tracing  cloth,  the  print  can  be  taken  in  as  soon  as 
the  meter  registers  that  particular  number.  Other 
brands  of  paper  will  require  a  different  meter  number, 


92  FERRIC   ASD   HELIOGRAPHIC   PROCESSES 

but,  these  once  ascertained  (by  a  test  exposure),  ex- 
posures can  be  made  with  certainty.  Several  frames 
can  be  timed  with  one  meter  if  exposed  at  the  same 
time  and  to  the  same  light.  The  meter  can  be  used 
also  for  Pellet,  ferro-gallic,  and  other  processes. 

Development. — On  removal  from  the  frame  the 
print  is  washed  in  water.  Slowly  running  water  is 
best,  but  in  its  absence  a  soft  brush  or  sponge  is  very 
efficient  in  removing  the  surplus  salts.  A  thorough 
treatment  in  this  way  in  the  first  water,  followed  by 
two  or  three  short  soaks  in  clean  water,  will  be  suffi- 
cient. Too  little  washing  causes  veiling  of  the  lines 
afterwards  :  too  much,  a  general  weakening  of  the 
copy.  Fifteen  to  twenty  minutes  is  generally  quite 
sufficient.     In  winter,  a  little  more. 

In  cases  where  a  print  is  required  at  the  earliest 
possible  moment,  lay  the  copy  in  the  bottom  of  the 
washing  bath  and  apply  a  vigorous  stream  of  water 
from  an  india-rubber  tube  (squeezing  the  end  between 
the  fingers  or  using  a  jet)  to  both  back  and  front  of 
the  paper.  A  minute  or  two's  treatment  of  this  kind 
suffices  to  get  rid  of  practically  all  the  soluble  salts. 

After  washing,  the  copy  is  rolled  up  wet  and  the 
roll  stood  up  to  drain  :  then  opened  out  and  hung 
up  to  dry  in  a  subdued  light. 

Over-printed  copies  are  given  a  somewhat  longer 
washing,  which,  if  exposure  has  not  been  greatly  ex- 
cessive, has  the  effect  of  clearing  the  lines  ;  other- 
wise, it  is  best  to  throw  away  the  prints  rather 
than  to  treat  them  with  potash  or  other  chemical 
reducing  agents,  the  results  of  which  are  generally 
disappointing. 


FERRO-PRUSSIATE,  OR  WHITE  LINE  ON  BLUE  GROUND    93 

Under-printed  copies  can  be  somewhat  improved  by 
immersion  is  a  weak  solution  of  an  iron  (ferric)  salt, 
though  no  great  intensification  must  be  expected. 
Scherings  make  up  a  solution,  specially  for  use  with 
their  blue  paper,  under  the  name  of  Verstclrkungslo- 
sung  fur  Blaus&ures  Uisenpapier.  Apparently  it  is 
an  iron  salt.     The  well  washed  print  is  placed  in — 

Stock  sol.,  .     2*5-5  mins.  5-10  c.cs. 

Water,       .         .  1  ounce.  1000    ,, 

for  about  five  to  twenty  seconds,  and,  as  soon  as 
the  blue  of  the  ground  has  deepened  sufficiently,  is 
washed  in  clean  water  and  dried.  The  weak  bath 
keeps  several  days.  The  usual  experience  is,  how- 
ever, that  intensification  is  of  little  use,  and  that  an 
under-exposed  print  had  better  be  thrown  away  and 
a  second  copy  made. 

Additional  lines  are  put  in  with  the  oxalate  of 
potash  solution  (given  on  p.  115)  thickened  with  a 
little  gum  arabic. 

Existing  lines  are  removed  by  Prussian  blue  applied 
with  a  fine  camel's-hair  penciL 


94  FEKRIC   AND   HELIOGRAPHIC    PROCESSES 


CHAPTEE    XIV 

Pellet,  or  Blue  Line  on  White  Ground 

The  Pellet  paper,  the  manufacture  of  which  is  de- 
scribed on  p.  68,  is  much  more  sensitive  than  most 
brands  of  ferro-prussiate,  and  must  only  be  handled 
in  quite  a  subdued  light.  The  exposure  in  summer 
sunlight  is  about  seventy  seconds,  but,  as  the  image 
is  only  faintly  visible,  it  is  necessary  to  judge  of  its 
completion  by  a  trial  method  or  by  meter,  as  de- 
scribed on  p.  90. 

Trial  Method.  — When  the  paper  is  being  placed  in 
the  frame,  a  test  strip  of  tracing  cloth  is  placed  along- 
side the  tracing.  This  strip  (which  may  measure 
about  6x2  inches)  has  ruled  upon  it  half  a  dozen  or 
more  lines  in  Indian  ink  or  vermilion,  corresponding 
as  nearly  as  may  be  with  the  lines  of  the  tracing,  the 
cloth  also  being  of  a  similar  quality.  A  stock  of 
these  strips,  in  different  thicknesses  of  ink  and  on 
different  cloths,  should  be  kept  at  hand,  and  with  a 
little  experience  it  is  easy  to  select  a  suitable  one. 
The  strip  is  laid  near  the  edge  of  the  frame,  and  a 
few  strips  of  sensitive  paper  laid  crosswise  behind  it 
with  the  free  ends  projecting  from  the  frame.  When 
the  exposure  is  judged  to  be  about  complete,  a  strip 
of  paper  is  pulled  out  and  the  frame  swung  over. 
The  strip  is  dipped   in   the   ferrocyanide   bath   for 


PELLET,   OR   BLUE   LINE   ON   WHITE   GROUND        95 

about  thirty  seconds.  The  lines  should  develop  to  a 
vigorous  blue,  and  the  ground  show  no  sign  of  blue 
stain.  If  the  ground  is  blue,  continue  the  exposure 
and  test  again.  If,  on  the  other  hand,  the  lines  are 
feeble  and  broken,  exposure  has  been  too  long. 

Faking  during  Printing. — During  exposure  to 
light  a  good  deal  can  be  clone  to  make  the  most  of 
inferior  tracings  by  masking  portions  of  the  latter. 
Very  often  one  part  of  the  tracing  is  made  in  thinner 
ink  than  another,  as  may  be  seen  by  holding  the 
tracing  up  to  strong  daylight,  and  the  thinner  parts 
will  be  saved  from  being  feebly  reproduced  by 
masking  with  a  soft  dark  cloth  which  can  be  readily 
fitted  to  the  area  desired.  Then  the  outside  parts  of 
the  tracing  are  liable  to  get  dirty  and  to  give  a 
bluish  ground,  if  exposure  be  timed  for  the  lines ; 
but  if  the  central  lined  portions  be  covered,  an 
additional  exposure  can  be  given  to  the  outside, 
which  will  ensure  a  pure  white  ground  in  the  copy. 

Develoiwwnt.  — The  print  is  developed  on  a  strong 
solution  of  potassium  ferrocyanide  (yellow  prussiate 
of  potash). 

Yellow  prussiate,     1  ounce.      1  pound.       100  grams. 
"Water,     .         .     10  ounces.     1  gallon.     1000  c.cs. 

Use  warm  water  for  dissolving  the  salt  and  see  that 
the  temperature  of  the  bath  does  not  fall  below  about 
60°  Fahr.  Some  makers  advise  rather  stronger, 
and  others  weaker  solutions  than  the  above.  Their 
printed  instructions  will  supply  the  specific  strength. 
The  developing  tray  should  contain  this  solution  to 
a  depth  of  from  f  of  an  inch  to  1  inch. 


96 


FEERIC   AND   HELIOGRAPHIC    PROCESSES 


Before  development,  turn  up  the  edges  of  the 
print  all  the  way  round  about  half  an  inch,  so 
that  it  forms  a  shallow  tray.  In  this  shape  it  is 
removed  and  floated  on  the  developer,  the  raised 
edge  preventing  the  access  of  developer  to  the  back. 
As  soon  as  laid  on  the  liquid,  the  whole  back  is 
smoothed  down  with  the  palm  of  the  hand  so  as  to 
bring  every  portion  into  contact  with  the  liquid 
(fig.    13).     Then  it   is   raised   by  the   two   nearest 


Developing  Pellet  Papers. 


corners,  and  held  up  for  examination.  All  the  lines 
ought  to  be  visible  in  vigorous  blue.  The  time  from 
the  moment  of  flotation  to  the  removal  from  the 
developer  should  not  exceed  about  thirty  seconds. 
Too  long  on  the  developer  produces  spreading  of  the 
lines. 

Washing. — Next  pass  the  print  into  a  bath  of 
water,  and  flush  it  quickly  back  and  front  from  the 
india-rubber  tube.     This  is  merely  to  stop  the  action 


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PELLET,   OR   BLUE   LINE    ON   WHITE    GROUND        97 

and   remove   most   of    the    ferrocyanide,    and   only 
occupies  a  few  seconds. 

Acid  Bath. — The  print  next  passes  into  an  acid 
bath  (sometimes  referred  to  as  the  '  fixing '  and 
sometimes  as  the  '  bleaching  '  bath).  This  is  made 
(in  an  earthenware  vessel)  as  follows  : — 

Sulphuric  acid  (sp.  )         „  ^^  4Q  ^ 

gr.  1-98),     .         ) 
Water,    ...       40    ounces.     1000     „ 

Add  the  acid  to  the  water,  and  not  vice  versa.  Much 
heat  is  produced  on  mixing,  so  that  a  glass  vessel 
must  not  be  used.  Instead  of  sulphuric  acid, 
hydrochloric  acid  can  be  used  : — 

Hydrochloric  acid,       .       4  ounces.        100  c.cs. 
Water,        .         .         .     40       „  1000    „ 

These  are  average  strengths,  but  the  makers' 
directions  will  give  those  which  they  consider  best  for 
their  papers.  Keep  the  prints  in  this  bath,  face  up, 
for  not  more  than  five  or  six  minutes,  occasionally 
stirring  the  liquid  with  a  wooden  spoon  or  with  a 
rag  tied  to  a  stick.  This  bath  soon  turns  a  deep 
blue,  but  retains  its  solvent  properties  (for  the 
insolubilised  gum)  for  a  long  time. 

Final  Washing.  — On  its  removal  from  the  acid  bath 
the  print  is  covered  with  a  deposit  of  light  blue  color, 
derived  from  the  oxidation  of  the  white  precipitate 
produced  by  ferrocyanide  on  ferrous  salts.  This 
deposit  is  only  loosely  adherent,  and  is  washed 
away  by  subjecting  the  print  to  a  stiff  jet  of  water. 

A  soft  brush  can  be  used  in  default  of  a  strong 


98      FERRIC  AND  HELIOGRAPHIC  PROCESSES 

enough  water  pressure,  but  requires  gentle  handling 
to  avoid  weakening  the  lines.  Be  particular  to 
keep  this  washing  bath  clean  by  regularly  scrubbing 
it  with  potass  solution  and  a  hard  brush.  Wash  the 
print  in  running  water  or  several  changes  for  a 
quarter  of  an  hour,   and  dry. 


Defects,  their  Causes  and  Remedies. 

Blue  Stains  in  Patches.  — 1.  Incomplete  contact  of 
the  print  with  the  developing  solution. 

2.  Developer  getting  on  the  back  of  print. 

3.  From    stained    fingers,    while    being    finally 
washed. 

Remedies. — Eemove  the  blue  stains  with  the 
oxalate   solution   given   on   p.   115. 

Be  careful  to  clean  the  fingers  in  weak  potass 
solution   after    dabbling   in   the   acid   bath. 

Uniform  Blue  Ground.  — Under-exposure. 

Faint  and  Broken  Lines.  — Over-exposure. 

Spread  and  Blurred  Lines. — Under-exposure.  Too 
long  development.     Too  strong  developer. 


FERRO-GALLIC,  OR  BLACK  LINE  ON  WHITE  GROUND      99 


CHAPTEE   XV 

Ferro-gallic,  or  Black  Line  on  White  Ground 

The  manufacture  of  the  sensitive  papers  has  already 
been  described  on  page  72. 

Gallic-Bath  Process — Exposure. — The  paper  is 
very  much  slower  (about  five  times)  than  Pellet 
paper,  and  requires,  in  summer  sunlight,  an  exposure 
of  about  five  minutes.  The  exposure  is  judged  by 
(1)  noticing  when  the  portions  of  paper  projecting 
outside  the  tracing  become  white.  A  corner  of 
the  sensitive  paper  is  folded  over,  so  that  the 
white  back  of  the  paper  provides  a  standard  for 
comparison.  (2)  Test  strip  as  described  on  p.  94, 
the  strip  being  immersed  in  the  gallic -acid  bath. 
(3)  Meter  (p.  90).  The  writer  prefers  (2)  and  (3) 
to  (1),  which,  with  tracings  of  yellowish  color,  is 
liable  to  give  under-exposed  proofs.  "Whichever 
method  is  used,  the  correctly  exposed  copy  is  seen  as 
yellow  lines  on  a  white  ground.  The  sooner  it  is 
developed  the  better,  but  it  should  certainly  not 
be  kept  over-night. 

Development. — Gallic  acid  is  the  developer  gener- 
ally used,  in  conduction  with  some  substance  to 
help  keep  the  ground  clear.  Alum  or  oxalic  acid 
(the  latter  in  small  proportion)  is  used  for  this. 


100  FERRIC   AND   HELIOGRAPHIC  PROCESSES 

An  average  formula  is  : — 


Gallic  acid, 

2  ounces. 

12  grams. 

Alum, 

•     2        „ 

12 

Water,    . 

1  gallon. 

1000  c.cs. 

Mix  in  warm  water  twenty-four  hours  before  use. 
Immerse  the  print  in  the  liquid  for  about  three 
minutes.  The  copy  develops  at  once  to  intense 
black  lines  on  the  ground,  which  is  never  quite 
white,  but  always  has  a  pale  violet  tint.  Wash  in 
running  water  for  a  few  minutes,  drain,  and  dry. 

Defects  and  Causes. — Violet  ground  with  thick  and 
blurred  lines — under-exposure.  Faint  and  broken 
lines — over-exposure. 

Water-Bath  Process. — Exposure  takes  place  just 
as  for  the  gallic-bath  paper,  and  development  must 
follow  on  the  same  day. 

Development. — Wash  in  running  water  for  ten 
minutes  or  so.  Under-  and  over-exposure  cause  the 
same  defects  as  with  gallic-bath  paper. 

Violet  spots,  lines,  and  unnecessary  dimensions 
are  removed  by  a  weak  solution  of  oxalic  acid. 

The  directions  given  for  the  use  of  the  ferro-gallic 
paper  made  by  Messrs  Messerli  of  Zurich  contain  a 
number  of  useful  hints  from  which  the  following  are 
quoted. 

The  pressure  pad,  whether  of  felt  or  cloth,  is  liable 
to  become  damp,  and,  when  placed  directly  on  the 
back  of  the  paper,  not  only  spoils  the  ground  of  the 
paper,  but  renders  a  much  longer  exposure  necessary. 
This  explains  the  considerable  difference  in  sensitive- 
ness sometimes  noticed  between  pieces  of  paper  from 


FERRO-GALLIC,  OR  BLACK  LINE  ON  WHITE  GROUND   101 

one  and  the  same  roll.  The  moist  condition  of  the 
frame  is  responsible  for  these  irregularities,  and  not, 
as  the  printer  may  be  inclined  to  think,  a  want  of 
uniformity  in  the  paper. 

The  fact,  too,  is  frequently  overlooked  that  the 
much  weaker  action  of  winter  sunlight  on  the  paper 
is  in  part  due  to  the  absence  of  heat  rays,  and  that, 
if  the  pressure  pad  of  the  frame  is  thoroughly 
warmed,  exposure  takes  place  appreciably  more 
quickly.  Before  ten  in  the  morning  and  after  one 
o'clock,  winter  sunlight  is  very  weak. 

It  is  a  mistake  to  be  over-economical  with  the 
developer,  which  should  be  renewed  as  soon  as  the 
printer  notices  that  the  developing  bath  is  becoming 
exhausted.  An  overworked  bath  will  not  give  an 
intense  black  tone. 

A  cause  of  failure  with  the  ferro-gallic  process  is 
in  floating  the  copy  on  the  developer  or  in  develop- 
ing by  drawing  through  the  solution.  Total 
immersion  is  necessary.  In  the  after- washing,  the 
copy  must  on  no  account  be  allowed  to  remain  long 
in  water  containing  developer.  The  best  way  to 
wash  is  to  hold  the  copy  for  five  minutes  under  a 
rose  jet,  so  that  the  water  continually  passes  off. 

Insufficiently  exposed  prints  can  be  corrected  by 
applying  a  2  per  cent,  solution  of  tartaric  acid  with  a 
sponge,  and  as  soon  as  the  dark  ground  has  given 
way,  by  well  washing  with  water.  This  treatment 
will  frequently  be  found  of  service,  and  the  solution 
should  find  a  place  in  every  printing  house. 

When  testing  a  fresh  batch  of  paper,  the  fact 
should  be  borne  in  mind  that  the  first  yard  or  so 


102  FERRIC  AND   HELIOGRAPHIC   PROCESSES 

of  the  roll  seldom  gives  such  good  prints  as  the 
remainder,  and  the  inferiority  of  the  first  portion  is 
the  more  noticeable  the  longer  the  paper  has  been 
kept.  A  freshly  made  developing  bath  should  be 
used,  and  if  the  paper  from  the  first  or  second  yard's 
length  does  not  give  good  results,  about  half  the 
paper  should  be  unrolled  and  a  piece  exposed  from 
the  middle  portion.  If  this  likewise  gives  poor 
results,  the  paper  may  be  assumed  to  be  at  fault. 


CHAPTEE    XVI 

Brown  Line  on  White  Ground 

This  paper,  made  as  described  on  page  73,  gives 
from  an  ordinary  tracing  a  copy  in  white  lines  on  a 
deep  brown  ground,  prints  very  rapidly,  and  requires 
very  simple  treatment  after  exposure.  The  brown 
color  of  the  deposit  makes  the  process  a  very 
suitable  one  for  preparing  several  paper  negatives 
from  a  single  tracing,  each  of  which  can  be  put  in 
hand  to  give  copies  in  blue  line  on  a  white  ground 
(on  ferro-prussiate  paper),  or  brown  lines  on  a  white 
ground  if  the  '  brown '  paper  itself  be  used.  For 
getting  a  number  of  prints  from  a  tracing  which  is 
wanted  at  once  for  some  other  purpose,  the  process 
is  therefore  most  useful. 

Moreover,  part  of  one  tracing  can  be  combined  in 


BROWN  LINE   ON  WHITE   GROUND  103 

the  copy  with  part  of  another  by  preparing  separate 
sepia  negatives,  pasting  the  parts  required  together, 
and  taking  copies.  In  this  way  the  sepia  negative 
is  useful  for  taking  off  copies  from  a  tracing  part  of 
which  has  to  be  modified  from  time  to  time. 

A  very  much  better  result  can  very  often  be 
obtained  vid  a  sepia  negative  and  a  '  negative ' 
paper  than  by  a  '  positive '  paper  printed  direct 
from  the  tracing. 

White  Line  on  Brown  Ground. — The  tracing  and 
paper  are  placed  in  the  frame  just  as  for  a  ferro- 
prussiate  print  and  exposed  to  light.  The  time  of 
exposure  in  summer  sunlight  is  from  thirty  seconds 
to  six  minutes.  The  appearance  of  the  print  when 
fully  exposed  is  a  clear  brown  :  it  gains  vigour  some- 
what in  washing  and  fixing. 

Washing. — Wash  the  print  for  about  five  minutes 
in  running  water. 

Fixing.  — The  fixing  bath  contains  : — 

Hypo,      .         .     7  grains.     4  ounces.         20  grams. 
Water,    .         .     1  ounce.      1  gallon.      1000  c.cs. 

and  in  this  the  print  is  immersed  for  about  a  minute. 
The   fixing   solution   can  be   applied,    if  more  con- 
venient, with  a  sponge  or  brush. 
A  fixing  solution  of — 

Soda  sulphite  cyst.,         .        1£  ounce.      150  grams. 
Water,  .         .         .         .10    ounces.     1000  c.cs. 

gives  a  print  of  darker  color  and  more  opaque  to 
actinic  light  than  the  hypo  (Namias).  But  it  is  at 
least  twenty  times  the  cost  of  hypo. 


104  FERRIC   AND  HELIOGRAPHIC   PROCESSES 

Final  Washing. — Well  wash  for  about  fifteen 
minutes,   and  dry. 

Brown  Line  on  White  Ground. — The  'brown  ground ' 
copies  obtained  as  just  described  can  be  used  for 
printing  positive  copies.  A  thin  paper  is  best  for 
this  purpose,  for  the  sake  of  rapidity  of  printing,  but 
a  thicker  paper  can  be  rendered  translucent  by 
means  of  castor  oil,  as  described  on  page  115.  The 
brown-ground  copy  is  treated  exactly  like  a  tracing, 
and  exposure  and  fixation  of  the  copy  proceeded 
with  as  above  described. 

To  remove  brown  lines  from  the  '  white  ground  ' 
prints,  or  to  insert  white  lines  in  the  '  brown  ground  ' 
prints,  use  a  solution  as  follows  : — 

Sat.    sol.   of   potass  )       ,  _      .  0  K 

r  >      15  mms.  35  c.cs. 

cyanide  in  water,    j 

Sat.    sol.    of  iodine  )  -.  9 

in  alcohol,        .J 

Water,        ...       1  ounce.       1000     „ 

Note. — Since  the  paragraph  on  page  73  was  written,  it  has  come 
to  the  writer's  knowledge  that  the  first  patent  for  a  sepia  process 
was  taken  out  by  Henry  Shawcross  in  Paris,  March  18th,  1889. 
Shawcross  took  out  a  similar  patent  (18,531,  1892)  in  England, 
but  did  not  mature  it. 


MINOR   HELIOGRAPHIC   PROCESSES  105 


CHAP  TEE    XVII 

Minor  Heliographic  Processes 

A  number  of  processes  of  minor  importance  are 
described  in  this  chapter.  Considerations  of  cost  or 
of  skill  demanded  for  working  them  have  prevented 
most  of  them  from  coming  into  general  use. 

Willis's  aniline  process  gives  dark  lines  on  a  white 
ground  from  an  ordinary  tracing,  and  depends  on 
the  fact  that  aniline  reacts  with  chromic  acid  to  form 
a  blue-black  coloring  matter.  It  has  been  used  in 
engineering  works  to  a  slight  extent. 

Paper  is  coated  with  a  chromate  mixture  and, 
after  exposure,  is  developed  in  aniline  vapour. 
Sensitise  a  hard  paper  (Steinbach)  by  floating  for 
one  minute  on — 

Potass  bichromate,  ....  1  part. 
Phosphoric  acid  (sp.  gr.  1-24).  .  10  parts. 
Water, 10     „ 

Dry  quickly,  and  expose  on  same  or  next  day. 
In  summer  sunlight  the  exposure  required  under  a 
tracing  is  about  three  minutes.  The  copy  appears 
in  yellow  lines  on  a  greenish  ground. 

To  develop,  the  print  is  placed  on  the  bottom  of 
a  shallow  box,  to  the  lid  of  which  are  pinned  several 


106  FEREIC   AND   HELIOGRAPHIC   PROCESSES 

sheets  of   blotting-paper,    soaked   in   a   mixture   of 
aniline  oil  and  benzene  : — 

Aniline,  about         ....        1  part. 
Benzene,  .         .         .         .         .15  parts. 

More  aniline  accelerates  development.  The  solu- 
tion is  spread  evenly  on  the  blotting-paper  and  the 
print  left  in  the  box  to  gradually  develop.  The 
correctly  exposed  copy  commences  to  appear  after 
a  few  minutes  and  gradually  gains  strength.  The 
final  tint  of  the  copy  is  influenced  by  the  time  of 
development.  Long  exposure  to  the  aniline  gives 
brownish-black,  whilst  the  shorter  the  development 
the  bluer  the  color.  The  prints  are  washed  in 
water  for  a  few  minutes.  During  this  treatment 
they  occasionally  turn  green  :  add  a  few  drops  of 
ammonia  to  the  wash  water.  In  the  industrial 
use  of  the  process  development  is  accelerated  by 
employing  a  steam  bath  to  volatilise  the  aniline. 

Poitevin's  process  utilises  the  fact  that  gelatine 
mixed  with  a  ferric  salt  is  insoluble  in  water,  but 
becomes  soluble  when  the  mixture  is  exposed  to 
light. 

The  following  working  details  are  due  to  Abney  : — 
Prepare  a  6  per  cent,  solution  of  gelatine  and  add 
sufficient  of  a  suitable  pigment.  Float  paper  on 
the  warm  mixture  and  sensitise  by  immersion  in — 

Ferric  chloride,         .     44  grains.       100  grams. 
Tartaric  acid,  .  13       „  30       „ 

"Water,    ...       1  ounce.     1000  c.cs. 

Dry   in    the    dark,    expose    with    the    aid    of    an 
actinometer,  and  develop  in  hot  water.     The  process 


MINOE   HELIOGEAPHIC   PROCESSES  107 

gives  a  copy  in  dark  lines  on  a  white  ground  from 
a  tracing,  and  while  it  furnishes  most  excellent 
reproductions,   requires  great  care  in  manipulation. 

Ferric-colloid  processes  have  been  very  little 
investigated,  although  they  offer  a  promising  field 
for  heliographic  papers. 

According  to  Lux,  *  ferric  chloride  and  tartaric  acid 
is  the  best  iron  mixture,  and  one  part  of  anhydrous 
ferric  chloride  should  be  used  to  every  four  parts  of 
gum  arabic  or  five  parts  of  gelatine.  One  formula  is 
as  follows  : — 100  parts  of  gum  arabic  are  dissolved 
in  200  parts  cold  water,  10  parts  of  tartaric  acid 
added,  and  then  in  small  doses  ferric  chloride 
solution  equivalent  to  25  parts  Fe2Cl6.  This  solution 
is  ready  for  use  twenty-four  hours  after  mixing,  but 
reaches  its  maximum  sensitiveness  in  about  three 
weeks.  Lux  adds  pigment  to  it  to  make  the  coating 
mixture,  taking  one  part  of  solid  pigment  to  about 
three  to  four  parts  of  solution. 

Ghromate  Pigment  Processes. — The  insolubility, 
etc.,  conferred  upon  gum  or  gelatine,  when  exposed 
to  light  with  potassium  bichromate  (see  p.  142)  is 
the  basis  of  several  processes  of  this  kind.  They 
give  copies  in  white  lines  on  a  dark  ground.  The 
first  two  of  the  processes  for  which  we  have  space 
depend  on  the  insolubilisation  of  gum. 

Prepare — 

Gum  arabic,     .  .     35  grains.         80  grams. 

Lampblack,      .  9       ,,  20       „ 

Water,    ...       1  ounce.     1000  c.cs. 

*  Dr  Lux,  Deutsche  Photographen  Zeituny,  1903,  Nos.  35  and 
37,  pp.  533  and  563. 


108  FERRIC  AND   HELIOGRAPHIC   PROCESSES 

Spread  this  mixture  with  a  broad  brush  on  the 
paper,  dry,  and  sensitise  immediately  before  use 
with — 

Potass  bichromate,     .     55  grains.     125  grams. 

Water,  ...  1  ounce.  1000  c.cs. 
This  solution  is  liberally  applied  to  the  back  of 
the  paper,  which  is  allowed  to  stand  for  a  few 
minutes,  and  the  coating  then  equalised  with  a 
brush  just  moistened  with  sensitising  solution. 
Coating  can  be  done  in  daylight,  but  the  paper 
must  be  dried  in  the  dark.  The  pigmented  side  of 
the  paper  is  laid  in  contact  with  the  tracing,  and 
exposed  to  light  till  the  lines  of  the  drawing  are 
visible  on  the  back.  This  requires  from  ten  to 
twenty  minutes  in  summer  sunlight.  The  exposed 
copy  is  dipped  for  a  minute  in  pure  water  and  laid, 
pigment  side  up,  on  a  glass  plate.  The  surface  is 
rinsed  with  a  jet  of  water,  removed  from  the  water, 
and  the  soluble  parts  of  the  image  gently  dislodged 
with  a  soft  brush.  This  leaves  the  copy  in  yellow 
lines  on  a  black  ground.  It  is  next  soaked  in  water 
for  several  hours  to  dissolve  the  chromium  salts, 
washed  in  clean  water,  and  dried.  To  obtain  posi- 
tive copies  (dark  lines  on  white  ground)  a  negative 
tracing  must  be  prepared  (p.  102). 

Gelatine  is  used  in  place  of  gum  in  a  similar  way. 

Positive  copies  are  obtained  from  tracings   by  a 

variation  of  the  method  due  to  L.  von  Itterheim  : — 

Gum  arabic,      .         .110  grains.     250  grams. 

Potass  bichromate,     .31       ,,  70       „ 

Alcohol,    ...       5  mins.         10  c.cs. 

Water,      ...       1  ounce.    1000    „ 


MINOR    HELIOGKAPHIC    PEOCESSES  109 

Smooth  sized  paper  is  coated  with  this  mixture, 
which  keeps  a  few  days.  It  is  exposed  under  a 
tracing  for  five  or  ten  minutes,  and  washed  in  water 
till  the  lines  of  the  drawing  look  engraved.  It  is 
then  dried,  and  given  an  even  and  thin  coat  of 
shellac  and  lampblack. 

Shellac, 1  part. 

Lampblack,     .....        3  parts. 
Alcohol, 20      „ 

Apply  this  with  a  sponge  and,  when  dry,  immerse 
the  paper  in — 

Sulphuric  acid,         ....   2-3  parts. 
Water, 100       „ 

until  the  superfluous  black  can  be  removed  by  gentle 
rubbing. 

In  this  process  a  ground  of  insoluble  gum  is 
formed  with  the  lines  of  the  tracing  in  soluble 
gum.  These  latter  are  removed  by  the  washing, 
and  when  the  shellac  is  applied,  the  bare  paper 
retains  it  whilst  the  ground  is  cleared  of  pigment 
by  the  weak  acid.  The  method  is  said  to  be 
commercially   worked   in   Vienna   (Eder). 

According  to  Valenta*  the  paper  for  Itterheim's 
and  like  processes  must  be  smooth  and  well  sized 
in  order  that  the  lights  shall  not  retain  the  soluble 
gum  and  chromate,  and  also  that  the  insolubilised 
gum-chromate  may  be  readily  removed  in  the  acid 
bath.  To  test  the  paper,  some  lines  are  ruled  on  it 
with  the  mixture  of   shellac  and  lampblack   to   be 

*  Pholographische  Korrespondenz,  Jan.  1904. 


110  FERRIC   AND  HELIOGRAPHIC   PROCESSES 

used  in  the  process  itself,  these  being  applied  with  a 
pen  or  a  fine  brush.  When  they  are  dry  the  paper 
is  placed  in  dilute  hydrochloric  acid  (1  in  50),  and 
left  there  for  some  hours.  If  the  strokes  are  easily 
removed  on  rinsing  in  a  stream  of  water,  or  gently 
treating  with  a  soft  wet  brush,  the  paper  is  un- 
suitable. As  a  test  for  the  proper  sizing  of  the 
paper  a  double  cross  is  drawn  on  the  paper  with  a 


pen  and  a  brilliant  ink  such  as  Chemnitz  violet 
copying  ink,  and  left  to  dry.  No  signs  of  the 
cross  should  be  visible  on  the  back  of  the  paper,  and 
the  edges  of  the  lines  should  be  quite  sharp.  If 
a  smooth  paper  withstands  both  tests  it  is  usually 
well  suited  to  the  process. 

These  methods  give  copies  of  fine  pigment  black 
on  a  white  ground  from  negatives  of  the  tracings. 
As  worked  by  E.  J.  Hall  &  Co.,  who  issue  a 
commercial  paper  based  on  this  principle,  the 
modus  operandi  is  greatly  simplified.  The  paper 
is  printed  from  the  negative  copy,  yielding  a  faint 
brown  image  on  a  yellow  ground.  Lampblack  in  a 
slightly  moist  state  is  then  rubbed  all  over  the  print 
with  a  pad,  and  the  paper  then  developed  in 
hot  water.  The  ground  of  soluble  gelatine  comes 
away,  but  the  lines  remain  as  fine  pigment  black. 
Messrs   Hall  claim  that  the  sensitive  {i.e.   bichro- 


MINOR  HELIOGEAPHIC  PROCESSES       111 

mated)  paper  will  keep  for  six  months   before   use 
as  ordinarily  wrapped. 

Pigment  paper  of  this  description  is  supplied  by 
Halden.  &  Co. ,  Manchester,  Bemrose  &  Co. ,  Derby, 
and  possibly  by  others.  Norton  &  Gregory,  West- 
minster, prepare  copies  by  a  secret  process  of  this 
kind  which  they  claim  to  be  a  development  of  the 
chromate  pigment  process,  differing  from  it  in  the 
colloid  used,  if  not  in  other  respects.  They  do  not 
supply  the  sensitive  paper. 

AnthraJcotype  depends  on  the  loss  of  tackiness  of 
gelatine  on  exposure  to  light  with  bichromate.  It 
was  devised  by  Sobacchi  in  1879  :  we  are  indebted  to 
Pizzighelli  for  precise  working  details.  The  process 
gives  a  positive  from  an  ordinary  tracing,  and  lines 
of  any  desired  color  can  be  obtained  by  selecting  a 
suitable  pigment. 

Hard  gelatine  is  mixed  with  cold  water  in  the 
proportion  of  one  part  of  gelatine  to  thirty  parts  of 
water,  allowed  to  swell  for  an  hour,  and  dissolved  by 
placing  the  containing  vessel  on  a  water  bath.  It  is 
filtered  and  kept  at  a  temperature  of  40-50°  C. 
(113-122°  Fahr.). 

Well-sized,  hard-surfaced  paper  is  cut  into  sheets, 
which  are  immersed  one  after  another  in  a  dish  of 
water.  A  thick  glass  plate  is  meanwhile  levelled, 
and  a  well-wetted  sheet  laid  thereon  :  a  piece  of 
sheet  rubber  is  laid  over  it,  and  the  two  squeegeed 
together.  The  rubber  is  removed,  and  the  edges  of 
the  paper  are  turned  up  all  round  about  half  an  inch. 
The  warm  gelatine  solution  is  poured  into  a  tray 
thus  formed,  and  by  tilting  the  glass  plate  and  with 


112  FERRIC   AND   HELIOGRAPHIC  PROCESSES 

the  help  of  the  finger  or  a  brush,  spread  over  the 
whole  surface.  This  done,  the  plate  is  set  aside  in  a 
horizontal  position  and  a  second  paper  coated,  the 
first  being  dried  as  soon  as  the  gelatine  has  set.  The 
gelatinised  papers  are  sensitised  in — 

Potass  bichromate,  .     18  grains.  40  grams. 

Water,    ...       1  ounce.      1000  c.cs. 

in  which  they  are  immersed  for  one  or  two  minutes, 
any  air  bubbles  being  detached  during  that  time  with 
a  camel's-hair  brush.  Sensitise  in  ordinary  day- 
light, but  dry  in  the  dark  :  the  paper  keeps  good  for 
a  week. 

Exposure  occupies  about  20-25  seconds  in  bright 
sunlight,  the  design  appearing  as  light  yellow  on  a 
brown  ground.  Over-exposure  can  be  corrected,  but 
not  under-exposure.  The  printed  proofs  are  washed 
in  several  changes  of  cold  water,  as  long  as  the  soluble 
bichromate  colors  the  solution  yellow.  Each  proof  is 
then  separately  dipped  in  a  bath  containing  water  at 
28-30°  Cent.  (84°-88°  Fahr. )  for  one  or,  at  most,  two 
minutes :  this  has  the  effect  of  slightly  softening  the 
lines  of  the  drawing  which  the  cold  bath  had  brought 
into  relief.  The  print  is  removed,  laid  face  up  on  a 
level  surface,  and  superfluous  moisture  blotted  off. 
Fine  pigment  is  now  dusted  over  the  paper  from  a 
fine  gauze  sieve  and  spread  over  the  lines  with  a  soft 
brush.  It  adheres  to  the  lines,  and  should  leave  the 
ground  white,  but  it  usually  happens  that,  owing  to 
insufficient  exposure,  the  ground  is  a  little  colored. 
Subsequent  washing  removes  this.  The  pigmented 
copy  is  next  dried  in  a  warm  place  (in  summer,  in  the 


BEMROSE'S  CARBON  PROCESS 

(Permanent). 


Particulars  on  application  to 

BEMROSE  &    SONS,  LTD., 
DERBY.  LEEDS  <S  LONDON. 


BEMROSE'S  CARBON  PROCESS 

(Permanent). 


Particulars  on  application  to 

BEMROSE  6  SONS,  LTD., 
DERBY,  LEEDS  6  LONDON. 


MINOR   HELIOGRAPHIC   PROCESSES  113 

sun  ;  in  winter,  near  a  fire  or  in  a  drying  oven)  at  a 
temperature  not  above  60°  C.  (140°  Fahr.).  It  is 
then  soaked  in  cold  water  till  limp,  the  ground  cleared 
from  superfluous  color  with  a  soft  wet  sponge,  and 
finally,  again  dried.  Many  pigments  can  be  used  : 
vegetable  black,  ultramarine  blue,  gold  and  silver 
bronzes,  all  give  good  results. 

Abney's  papyrographic  process,  a  form  of  collotype, 
depends  on  the  fact  that  gelatine  plus  bichromate,  on 
exposure  to  light,  acquires  the  property  of  retaining 
fatty  ink,  and  is  specially  suitable  for  taking  a 
number  of  copies  from  one  tracing.  Stout  paper  is 
floated  for  two  minutes  on — 


Potass  bichromate,  . 

13  grains. 

30  grams. 

Gelatine, 

26 

60      „ 

Water,     . 

1  ounce. 

1000      „ 

It  is  hung  up  to  dry  and  again  floated,  being  this 
time  hung  up  to  dry  in  a  position  opposite  to  the 
first.     Drying  must  take  place  in  the  dark. 

After  exposure  the  print  is  immersed  in  a  dilute 
solution  of  alum  to  remove  the  greater  part  of 
the  soluble  chr ornate.  It  is  then  placed  in  a  glass 
or  zinc  plate,  and  surface  moisture  removed  with 
blotting-paper.  It  is  then  inked  with  lithographic 
ink,  applied  with  a  soft  leather  or  velvet  roller,  and 
soaked  in  water  till  all  soluble  chromate  is  removed. 
The  design  is  left  in  black  lines  on  a  white  ground. 
From  this  print  forty  to  fifty  copies  can  be  taken  in 
an  ordinary  copying  press,  the  print  being  inked  for 
each  impression. 

With  Silver  Salts. — Papers  (plain  or  albumenised) 


114  FERRIC   AND   HELIOGRAPHIC   PROCESSES 

sensitised  with  silver  nitrate,  chloride,  or  other  salts, 
have  been  used  for  heliographic  copying,  giving  a  copy 
in  white  lines  on  a  dark  ground  from  an  ordinary 
tracing.  Those  who  wish  to  employ  a  silver  process 
will  find  it  better  to  use  the  commercial  sensitised 
paper  rather  than  to  prepare  one  for  themselves. 
The  only  use,  however,  to  which  present-day  copyists 
are  likely  to  put  the  process  is  in  preparing  the 
negative  from  a  small  tracing,  from  which  to  print 
positive  copies  on  ferro-prussiate  or  albumenised 
paper. 

Directions  for  working  the  process  will  be  found 
in  any  of  the  larger  treatises  on  photography.* 

Liesegang  j-  describes  a  rapid  silver  paper — con- 
taining silver  chloride  and  iodide  and  developed  with 
gallic  acid — which  is  capable  of  being  utilised  in 
everyday  work  to  some  advantage. 

*  Abney's  Instruction  in  Photography ;  Eder's  Handbuch  der 
Photographic  For  sensitising  formulae  and  brief  instructions, 
see  also  The  Figures,  Facts  and  Formulae  of  Photography. 

t  Die  modernen  Lichtpausverfahren,  p.  31. 


PRINTING   HOUSE   MEMORANDA  115 


CHAPTEK    XVIII 

Printing  House  Memoranda 

To  Oil  Drawings  on  Paper  for  Printing.  — 

Castor  oil,  .         .         .         .         .  3  parts. 

Alcohol,      .  .         .         .         .         10      „ 

Lay  the  paper  face  down  on  a  glass  plate  and  rub 
in  the  above  solution  with  a  small  sponge.  Warm 
before  a  stove  to  allow  the  oil  to  thoroughly  soak  in. 
When  the  paper  has  become  transparent  remove  all 
superfluous  oil  with  a  clean  rag  or  blotting-paper,  and 
again  warm.  The  paper  can  be  restored  to  its  original 
condition  by  soaking  in  alcohol  once  or  twice,  and 
then  in  water  mixed  with  alcohol. 

Another  method  is  to  iron  paraffin  wax  into  the 
warm  and  dry  paper  with  a  hot  iron.  Eemove 
surplus  wax  by  rubbing  with  a  soft  cloth. 

Potash  Oxalate  Solution  for  removing  Stains. — 

Potass  oxalate,       1  part.       75  grains.        170  grams. 
Water,  .         6  parts.       1  ounce.     1000  c.cs. 

This  solution  at  once  removes  the  blue  image  from 
both  ferro-prussiate  and  Pellet  prints.  The  paper 
should  be  afterwards  well  washed  :  if  this  is  not  done, 
the  blue  color  is  very  liable  to  reappear  in  course  of 
time. 


116 


FEEEIC  AND  HELIOGEAPHIC  PEOCESSES 


For  use  on  a  pen  the  solution  is  thickened  with  a 
little  gum  arabic,  though,  unless  the  draughtsman 
sends  the  copies  back  to  the  printing  house  to  be 
again  washed,  he  had  better  put  in  white  lines  on 
ferro-prussiate  prints  with  Chinese  white. 

Mounting  Prints. — To  mount  on  linen,  paste  the 
back  of  the  copy  thoroughly  well  with  fresh  flour 
paste  and  leave  for  five  or  ten  minutes.  Tack  the 
linen  tightly  to  a  smooth  table  and  gently  lower  the 
pasted  print  upon  it.  Eoll  a  duster  round  a  piece  of 
wood  to  make  a  firm  but  soft  pad,  and  rub  the  paper 
into  contact,  working  from  the  middle  in  all 
directions. 

To  Varnish  Mounted  Copies. — G-ive  a  coat  of  size 
(1  part  of  glue  dissolved  in  10  parts  of  water),  and, 
when  dry,  varnish  as  evenly  as  possible  with  a  good 
'  oak  '  or  '  church  '  varnish. 

Sizes  of  Drawing  Papers.  — 


Demy,    . 

.     17  x  22  inches 

Royal,    . 

.     20x25       „ 

Cartridge, 

.     21x26       „ 

Double  crown, 

.     20  x  30       „ 

Imperial, 

.     22  x  30       „ 

Double  demy, 

.     22x35       „ 

Double  elephant,    . 

.     27  x  40       „ 

Antiquarian,  , 

.     31x53       „ 

MANIPULATION  117 


CHAPTEK    XIX 

Manipulation 

Weights  and  Measures. — Since  making  up  solutions 
enters  very  considerably  into  the  working  of  the 
processes  described  in  these  pages,  the  question  of 
weights  and  measures  may  be  appropriately  mentioned 
under  this  heading.  In  almost  every  instance,  both 
metric  and  English  units  are  given,  but  the  writer 
strongly  advises  the  reader  to  work  by  the  metric. 
A  set  of  weights  from  50  grams  to  1  gram  can  be 
bought  for  one  shilling  and  threepence.  The  frac- 
tional parts  of  the  gram — "5,  "3,  '2,  and  *1 — can  be 
cut  out  of  aluminium  foil,  or  a  second  set  from  10 
grams  to  '01  gram  only  costs  another  eighteenpence. 
A  250  c.c.  measuring  cylinder  costs  about  two  and 
threepence,  whilst  a  wide-mouth  bottle  of  about  35 
to  40  ounces  capacity  can  be  marked  with  a  diamond 
for  a  litre  measure,  or  a  cylindrical  litre  measure 
bought  for  about  five  shillings. 

The  readiness  with  which  large  or  small  quantities 
of  a  solution  can  be  at  once  compounded  from  the 
formula  will  convince  the  photographer  of  the 
superiority  of  the  decimal  over  the  English  system. 

Hydrometers. — When  working  on  a  large  scale, 
particularly  when  chemicals  (like  ferric  chloride)  of 


118 


FERRIC  AND   HELIOGRAPHIC  PROCESSES 


indefinite  composition  are  being  used,  it  is  often 
advisable  to  adjust  the  strength  of  the  solution  by 
the  hydrometer,  as  is  done  in  the  case  of  the  Pellet 
sensitiser  given  on  page  69.  Hydrometers  measure 
the  specific  gravity  of  the  liquid,  and  are  made  to 
cover  a  certain  range  of  specific  gravity,  say,  1  "00- 
1  -20,  1  -20-1  -40,  and  so  on.  They  cost  about  half- 
a-crown  each.  The  specific  gravity  of  every  liquid 
varies  with  the  temperature,  and  it  is  therefore  usual 
to  adopt  the  temperature  of  60°  Fahr.  (15° '5  C.)  as 
that  at  which  the  gravity  is  to  be  taken.  If  the 
temperature  of  the  solution  differs  more  than  a  few 
degrees  from  this,  the  containing  vessel  is  placed  in 
warm  or  cold  water,  as  required. 

Baume 's  hydrometer,  which  is  much  used  on  the 
Continent  and  in  America,  is  differently  graduated  : 
its  zero  mark  corresponds  with  specific  gravity  of 
1 -00.  The  following  figures  give  the  gravities  equiv- 
alent to  degrees  Baume  : — 


Baume. 

Sp.  Gr. 

Baume. 

Sp.  Gr. 

30 

1-256 

40 

1-375 

31 

1-267 

41 

1-388 

32 

1-278 

42 

1-401 

33 

1-289 

43 

1-414 

34 

1-300 

44 

1-428 

35 

1-312 

45 

1-442 

36 

1-324 

46 

1-456 

37 

1-337 

47 

1-470 

3S 

1-349 

48 

1-485 

39 

1-361 

49 

1-500 

MANIPULATION 


119 


Filtering.  — Many  of  the  solutions  specified  in  these 
pages  require  filtering,  if  spotless  results  are  to  be 
obtained,  and  as  many  readers  may  never  have  fitted 
a  filter  paper  into  its  funnel,  one  or  two  words 
on  the  right  way  to  do  this  are  given  here.  A 
suitable  filter  paper  is  Ehenish,  No.  597,  made  by 
Schleicher  and  Schull,  and  obtainable  at  any  chemi- 
cal dealers  in  packets  of  100  circular  papers  from 


Fig.  14.— Filtration. 

3  inches  diameter  upwards.  The  way  in  which  the 
paper  is  fitted  into  the  glass  funnel  has  a  good  deal 
to  do  with  the  rapidity  of  filtration.  First,  fold  the 
circular  paper  into  two,  and  then  again  into  four, 
making  the  last  crease  lightly.  Place  the  paper  in 
the  dry  funnel,  and,  gently  placing  the  finger  in 
the  cone  of  the  paper,  see  what  amount  of  play  is 
possible.     The  filter  ought  to  '  waggle  '  to  and  fro 


120 


FERRIC   AND   HELIOGRAPHtC   PROCESSES 


about  a  quarter  of  an  inch.  If  the  first  folding  does 
not  give  this,  try  again,  laying  down  one  edge  of  the 
semicircular  paper  a  little  short  of  the  other  and  open- 
ing out  the  filter  to  form  a  cone  of  angle  greater  or  less 
than  60°  as  required.  Place  in  the  funnel,  and  press 
down  the  three-fold  side  of  filter,  so  that  the  single 
thickness  of  paper  is  pushed  against  the  glass  on  the 
opposite  side  and  the  point  of  the  filter  is  turned  away 
from  the  three-fold  side.     Now,  holding  the  funnel  in 


Fig.  15. — Coating  Paper  by  Floating. 

the  hand,  single  paper  lowermost,  pour  water  into 
the  filter  on  the  single  side,  bring  into  the  vertical 
position  and,  taking  hold  of  the  two  sides  of  the 
filter  at  the  points  where  the  single  and  treble 
thicknesses  meet,  slightly  lift  up  the  paper.  The 
stem  will  at  once  fill  with  water  and  filtration 
will  proceed  rapidly.  Though  taking  some  time  to 
describe,  the  operation  only  occupies  a  few  seconds. 

Coating  Paper. — This  is  done  either  by  floating  on 
the  solution  or  by  brushing  the  solution   over   the 


MANIPULATION 


121 


paper.  The  latter  method,  inasmuch  as  it  dispenses 
with  large  dishes  and  much  solution,  will  commend 
itself  to  the  photographer  who  only  wants  a  small 
batch  of  paper.  On  the  other  hand,  some  solutions 
give  a  much  more  even  coating  by  floating  than  by 
brushing. 

(a)  By  Flotation.  — To  float  the  paper  hold  the  sheet 
by  opposite  ends  in  a  loop  and  gently  lower  the 
middle  of  the  piece  till  it  touches  the  surface  of  the 
liquid.     By  lowering  the  hand,  the  paper  is  gradually 


Fig.  16. — Withdrawing  Paper  after  Coating. 

brought  on  to  the  surface  of  the  liquid  so  as  to  expel 
air  bubbles  (fig.  15). 

When  withdrawing  the  paper,  a  good  plan  is  to 
lay  a  piece  of  glass  rod  across  one  end  of  the  dish 
and  to  slowly  draw  the  paper  over  it.  This  removes 
superfluous  liquid  as  well  as  covers  any  minute  air 
bubbles  left  after  flotation  (fig.  16).  The  time  of  flota- 
tion varies  with  different  papers  and  baths  and  with 
the  degree  of  impregnation  desired.  When  one  wants 
to  keep  the  coating  as  much  as  possible  on  the  surface 
of  the  paper,  it  is  better  to  float  for  a  short  time,  to 
dry,  and  refloat,  rather  than  to  expose  the  paper  to 
a  more  protracted  flotation. 


122  FERRIC   AND   HELIOGRAPHIC   PROCESSES 

(b)  By  Brushing. — Soft  camel's  or  badger-hair 
brushes  of  good  size  are  often  used,  but  for  many 
solutions  the  writer  prefers  a  fine  Turkish  sponge  or 
a  piece  of  cotton-wool,  clean  and  free  from  grit.  A 
Blanchard's  brush  is  another  convenient  tool.  A 
piece  of  glass  plate  about  6x3  inches  has  a  strip  of 
swansdown  calico  or  Canton  flannel  folded  over  one 
end  and  secured  with  an  elastic  band  (fig.  17). 

After  use,  brushes  and  sponges  should  be  well 
washed  before  being  exposed  to  daylight.  The  cotton- 
wool and  the  material  in  the  Blanchard  brush  are 
used  fresh  each  time. 

When  applying  the  sensitising  solution,  it  is  almost 


Fig.  17. — Blanchard's  Brush. 

always  necessary  to  keep  the  brush  or  sponge  only 
just  wet  enough  to  give  a  thin  coating.  Too  much 
liquid  on  the  paper  means  a  fiat  sunken  image. 
Give  the  paper  steady,  even  strokes  in  one  direction 
and  then  crosswise.  Streaks  must,  of  course,  be 
avoided  as  much  as  possible,  but  it  is  not  at  all 
difficult  to  coat  paper  with  satisfactory  uniformity. 

Drying  in  a  proper  manner  is  important.  It 
should  be  quick,  but  the  paper  must  not  get  hot,  or 
fogged  images  may  result.  Some  papers  can  be  dried 
at  a  short  distance  from  a  fire,  but  it  is  more  satis- 
factory to  use  a  drying  oven.  This  need  not  be  at  all 
an  elaborate  or  expensive  affair  (for  work  on  a  small 


MANIPULATION  123 

scale),  and  below  are  given  the  figure  and  description 
of  one,  constructed  on  the  lines  of  one  described  by 
Mr  Alexander  Cowan  in  the  Photographic  Year  Book 
for  1881. 

A  box  of  suitable  size  is  made,  and  a  central 
aperture  about  2|  inches  diameter  made  in  top 
and  bottom.  The  upper  aperture  carries  a  length 
of  stove  piping  in  which,  at  about  one  foot  above 
the  box,  a  small  Bunsen  burner  is  fixed.  A 
|-inch  Fletcher's  burner  (price  sevenpence  with- 
out stand)  answers  well,  and  is  screwed  into  a 
right-angled  piece  of  tube,  passing  through  the 
pipe.  A  small  shutter  is  made  in  the  pipe  alongside 
the  burner,  for  conveniently  lighting  the  latter. 
To  the  lower  aperture  an  inverted  funnel-shaped 
vessel  is  attached,  made  of  tin-plate  and  fixed  by  a 
flange  to  the  under  side  of  the  box.  From  the  side 
of  this  vessel  a  short  length  of  stove  pipe  projects. 
The  funnel  is  filled  with  fragments  of  asbestos,  as 
used  in  gas  fires.  The  interior  of  the  box  is  pro- 
vided with  shelves  of  wood  frames,  covered  with 
linen,  on  which  the  sensitive  papers  are  laid  to  dry. 
These  shelves  are  removable,  and,  if  desired,  the 
paper  can  be  suspended  to  dry,  by  pinning  it  to  a 
cross-piece  of  soft  wood  (about  half-inch  square 
section)  and  laying  this  on  the  supports  of  the 
top  shelf.  A  hinged  or  sliding  door  is  fixed  to 
the  front,  and  the  whole  is  supported  on  four 
light  iron  legs,  so  as  to  leave  the  base  of  the 
funnel  about  twelve  inches  above  the  floor.  An 
oil  stove  placed  immediately  below  warms  the  air 
passing  through  the  chamber  containing  the  asbestos, 


124 


FERRIC    AND   HELIOGRAPHIC   PROCESSES 


whilst   the  draught  is   increased  by  the  burner   in 
the  chimney. 


Fig.  18. — Drying  Cupboard. 
The  air  enters  the  cupboard  on  the  right,  passing 
through  the  chamber  shown  packed  with  asbestos  balls, 
which  are  kept  warm  by  the  oil  stove. 


MANIPULATION  125 

The  use  of  the  burner  alone  enables  a  current  of 
cold  air  to  be  drawn  through  the  apparatus.  A  very 
moderate  increase  in  the  temperature  of  the  air  is 
sufficient  to  make  paper,  coated  by  notation  or 
brushing,  bone  dry  in  half  an  hour. 

Storage. — While  the  best  results  with  almost  all 
the  processes  here  described  are  obtained  on  freshly 
prepared  paper,  it  is  often  necessary  to  store  it. 
Damp  is  the  enemy  of  these  papers,  and,  if  they  are 
to  keep  well,  it  must  be  excluded.  A  calcium 
chloride  tube  is  the  best  receptacle,  though  it  need 
not  necessarily  be  of  the  form  sold  by  the  photo- 
graphic dealers.  Many  household  commodities  are 
supplied  in  tins  with  almost  hermetically  sealing 
lids,  and  it  is  only  necessary  to  divide  off  a  small 
portion  of  the  interior  (to  hold  the  calcium  chloride) 
to  have  an  efficient  storage  box. 

To  use  calcium  chloride  to  the  best  advantage  it  is 
mixed  with  asbestos.  Soak  commercial  asbestos  in 
a  strong  solution  of  the  chloride,  make  the  pasty 
mixture  into  little  pats,  and  dry  on  the  moderately 
warm  part  of  the  top  of  the  stove.  Gradually  move 
to  a  hotter  part,  till  the  pats  are  dry  right  through, 
and  store  in  a  stoppered  bottle  for  use.  When  these 
balls  become  damp  they  have  only  to  be  reheated  on 
the  stove  to  fit  them  for  use  again. 


126  FERRIC   AND   HELIOGRAPHIC   PROCESSES 


CHAPTEE   XX 

Paper  and  Sizing 

One  of  the  advantages  of  the  processes  described  in 
these  pages  is  the  facility  with  which  the  sensitising 
solutions  can  be  applied  to  all  kinds  of  papers,  so 
that  quite  a  variety  of  differently  surfaced  and  tinted 
papers  are  placed  at  the  photographer's  disposal  for 
printing  purposes.  The  ferro-prussiate  process  can 
be  worked  with  much  commoner  kinds  of  paper  than 
others,  such  as  Kallitype ;  but  among  good  quality 
papers  there  is  plenty  of  opportunity  for  the  exercise 
of  taste,  and  the  newer  school  of  pictorial  photog- 
raphers will  no  doubt  find  great  possibilities  in 
ringing  the  changes  on  tint  of  paper  and  color  of 
image. 

Among  raw  papers  the  well  known  brands  of  Saxe 
and  Eives,  long  used  for  albumenised  paper,  need  no 
introduction  to  the  student  of  photography.  They 
are  sold  in  sheets  18  x  22  inches,  and  can  be  used 
without  additional  sizing,  though  in  almost  every 
process  a  second  sizing  will  do  no  harm,  and  will 
generally  benefit  the  resulting  paper  as  regards 
rapidity  and  brilliancy  of  image.  Saxe  and  Eives 
paper  can  be  obtained  at  some  large  photographic 
depots,  and  as  the  raw  paper  is  not  in  very  frequent 
demand  it  is  as  well  to  specify  '  un-albumenised  ' 
when  ordering  it. 


PAPER   AND    SIZING  127 

Whatman's  drawing  papers,  supplied  in  three 
grades  of  surface,  are  very  suitable  both  for  large 
and  small  work.  They  are  supplied  in  the  various 
sizes  used  in  drawing  offices  as  given  on  page  116. 

Some  prices  are  here  given  as  a  guide  to  ordering : — 


Per  sheet. 

Per  quire, 

s.      d. 

s.     d. 

Demy,      . 

HP,  1ST. 

o    li 

3     0 

Royal, 

HP,  N,  R. 

0     3 

6     0 

Imperial, 

HP,  N,  R. 

0     5 

9     9 

,,          thick, 

HP,  N,  R. 

0     71 

14     3 

,,          extra  thick, 

HP,  N,  R. 

1     0 

22     6 

Double  elephant, 

HP,  jSt,  R. 

0  10 

19     0 

The  letters  in  column  2  indicate  the  surfaces  in 
which  each  size  is  made.  HP  is  hot  pressed  or 
smooth  ;  1ST,  not  pressed  or  natural  grain  ;  E,  rough. 

Cartridge  papers,  too,  are  very  suitable,  and  can 
be  had  in  a  variety  of  tones  and  sizes  from  large 
stationers  such  as  George  Gill  &  Sons,  of  Charter- 
house Street. 

Beeves  &  Son,  and  other  artists'  dealers,  stock  a 
few  French  drawing  papers  which  are  used  for  gum- 
bichromate  work.  The  brands  are,  Allonge,  Canson 
(18  different  tints),  Michallet  and  Ingres  (5  tints). 
Of  these  Michallet  and  Ingres  are  papers  of  peculiar 
texture,  and  take  the  ferro-prussiate  and  Kallitype 
solutions  very  well  :  with  the  other  two  brands  the 
writer  gets  degraded  lights,  though  possibly  the 
pictorial  worker  may  sometimes  be  able  to  make 
effective  use  of  this  property. 

Other    artists'    papers   which   have    been    found 


128  FEKEIC    AND    HELIOGRAPHIC   PROCESSES 

suitable  for  photographic  use  are  Wrigley's  imperial 
amber  antique  rough  surface  boards,  Dutch  hand- 
made Van  Gelder  (obtainable  in  several  textures  from 
the  London  agents,  Grosvenor,  Chater  &  Co. ,  Cannon 
Street,  E.  C. ),  and  Japanese  proof  papers.  * 

Albumenised  paper  (unsensitised,  of  course)  takes 
the  ferro-prussiate  and  other  solutions  perfectly,  and 
gives  very  fine  brilliant  prints. 

Better-class  hard-surface  writing  papers  may  be 
used.  A  local  stationer  or  printer  will  supply 
these. 

For  engineering  purposes,  where  large  tracings  are 
to  be  copied,  it  is  imperative  to  use  a  stout  paper. 

A  common  or  thin  paper  means  great  risk  of 
tearing  the  print  during  washing.  Special  tough, 
hard-surfaced  papers  are  made  for  the  purpose,  in 
various  degrees  of  stoutness — extra  stout,  stout, 
thin,  and  extra  thin.  The  lighter  kinds  are  suited 
for  sending  through  the  post,  or  for  making  copies 
to  be  subsequently  used  as  negatives  (page  102).  The 
heavier  brands  stand  the  wear  and  tear  of  shop  use 
better.  They  are  supplied  in  rolls  of  30  inches  wide 
and  upwards.  Steinbach  (London  agents,  Otto 
Konig  &  Co.)  makes  good  brands  suitable  for  the 
various  heliographic  processes. 

While  very  cheap  papers  can  be  employed  for  blue 
printing,  if  well  sized  and  used  fresh,  it  should  be 
borne  in  mind  that,  for  a  sensitive  paper  to  keep, 
sizing  must  be  reduced  to  a  minimum.  Hence  a 
pure,  hard-surfaced,  close-grained  paper  becomes 
necessary,  if   the  coated  paper   is  to  be   kept   any 

*  E.  Sanger  Shepherd,  The  Photogram,  1896,  p.  190  (Aug.). 


PAPER   AND   SIZING  129 

length  of  time,  but  when  it  is  convenient  to  use  the 
paper  within  a  few  days  of  its  being  coated,  it  is 
quite  easy  to  secure  equally  good  results  on  much 
cheaper  papers.  Light-colored,  heavy  manilla 
wrapping  paper,  used  for  newspapers  and  magazines, 
can  be  used,  with  this  qualification. 

Keeves  &  Son  supply  a  fabric  (Linaura)  resembling 
tracing  cloth  which  takes  the  ferro-prussiate  solu- 
tions quite  well.  It  is  practically  untearable  and 
uninjured  by  moisture,  whilst  the  sensitised  fabric 
is  said  to  keep  in  good  condition  for  a  much  longer 
time  than  similarly  coated  paper.  It  is  sold  in  rolls 
36  inches  and  42  inches  wide. 

Sizing  fills  up  the  pores  of  the  paper,  keeps  the 
image  on  the  surface,  and  so  prevents  flat  and 
sunken  prints.  Besides  this,  the  presence  of  the 
organic  body — gum,  starch,  or  gelatine — probably 
acts  in  many  instances  as  a  '  sensitiser  '  of  the 
sensitive  compound,  conferring  greater  sensitiveness 
upon  the  paper. 

The  most  effective  and,  for  the  amateur,  most 
convenient  method  of  sizing  is  with  arrowroot,  as 
described  by  Duchochois. 

Take- 
Arrowroot,  .  .        9  grains.  20  grams. 
Glucose,     .          .         .       2      ,,  5       „ 
Water,       ...       1  ounce.       1000  c.cs. 

Mix  the  glucose  and  arrowroot  with  a  little  cold 
water,  add  the  remainder  hot,  and  boil  up  the  whole 
in  a  porcelain  dish.  A  cheap  methylated  spirit 
lamp  (fig.  19)  is  very  convenient  for  this  purpose, 

9 


130 


FERRIC   AND   HELIOGRAPHIC   PROCESSES 


and  will  be  found  very  useful  on  many  other 
occasions.  An  ordinary  '  Granitine '  developing 
dish  can  be  used  instead  of  the  evaporating  basin 
shown  in  the  figure,  though  the  latter  is  handier  in 
use.  Stir  ail  the  time  heat  is  being  applied,  with  a 
spooon  or  glass  rod.  As  soon  as  the  liquid  boils 
extinguish  the  lamp  and  place  the  basin  in  a  large 
dish  of  water  to  cool.  Eemove  the  skin  from  the 
surface,   and  strain  through  fine  canvas. 


Fig.   19. — Spirit  Lamp  for  making  Size. 

The  necessary  number  of  sheets  of  paper  are  nailed 
down  by  the  four  corners  to  a  board  about  half  an 
inch  smaller  each  way  than  the  paper.  Obtain 
three  soft  Turkish  sponges  :  rinse  them  in  water  : 
with  one  take  up  a  little  arrowroot  solution,  and, 
using  it  lengthways  and  crossways,  spread  the  thin 
paste  into  an  even  layer.  Then  with  the  second 
sponge  rub  very  lightly  over  the  coating  so  as  to 
spread  it  as  evenly  as  possible.  Take  off  any 
excess   of   paste   with   the   third   sponge. 


PAPER   AND   SIZING 


131 


Gelatine  Sizing.  — 


Hard  gelatine,    . 

.  150  grains. 

9# 5  grams. 

Water, 

30  ounces. 

850  c.cs. 

Alum, 

.     45  grains. 

3  grams, 

Methylated  spirit, 

7  ounces. 

200  c.cs. 

Soak  the  gelatine  in  the  water  for  half  an  hour,  pour 
off  the  water  into  another  vessel,  and  heat  it  in  a 
water  bath  to  140°  F.  Then  pour  back  over  the 
gelatine,  and  when  the  latter  is  dissolved  add  the 
alum  dissolved  in  a  little  water,  and  lastly  the 
spirit ;  common  methylated  spirit  precipitates 
mineral  naphtha  when  mixed  with  water,  so 
that,  unless  the  unmineralised  spirit  can  be  used 
(and  this  is  obtainable  only  in  rather  large 
quantities),  absolute  alcohol  had  better  be  substi- 
tuted. Gently  draw  the  paper  into  this  solution, 
avoiding  air-bells  ;  soak  for  two  or  three  minutes, 
dry  quickly,  re-immerse  as  before,  and  again  dry, 
this  time  hanging  up  the  paper  by  the  two  opposite 
corners. 

Gum  arabic — a  few  grains  per  ounce — can  also  be 
used  as  size,  and  is  brushed  over  the  paper. 

'  Gloy, '  a  commercial  paste,  makes  a  good  size 
according  to  Mr.  Thomas  Manly,  in  a  letter  to  the 
writer.     It  is  neutral  and  keeps  well. 


132  FERRIC   AND   HELIOGRAPHIC   PROCESSES 


CHAPTEE    XXI 

Chemicals 

The  ferric  salts  are  the  compounds  chiefly  used  in 
the  processes  described  in  these  pages,  and  some 
space  may  therefore  be  devoted  to  the  preparation 
and  properties  of  these  and  several  other  equally 
important  substances. 

Ferric  chloride  may  be  purchased  in  three  forms  : 
(1)  anhydrous  (sublimed) ;  (2)  crystallised  or  solid ; 
(3)  in  solution. 

The  anhydrous  salt  forms  small  dark  green  crystals, 
which  absorb  water  from  the  air  with  the  utmost 
readiness.  Its  cost  is  considerably  greater  than  the 
other  forms  in  which  the  salt  is  sold,  but  for  use 
on  a  small  scale  it  has  the  advantage  of  definite- 
ness  of  composition  so  long  as  it  is  kept  well 
stoppered. 

Crystal  or  solid  ferric  chloride  is  sold  in  large 
yellow  lumps  also  very  deliquescent.  Their  com- 
position corresponds  approximately  to  Fe2Cl6. 12H20, 
equivalent  to  very  nearly  60  per  cent,  of  anhydrous 
chloride.  Whenever  '  ferric  chloride  '  is  prescribed 
in  a  formula  without  further  specification,  it  may  be 
taken  that  this  crystal  form  is  meant. 

Solution  of  Ferric  Chloride. — Ferric  chloride  is  a 
most    soluble    salt,    and    solutions    up    to    syrupy 


CHEMICALS 


133 


consistency  can  be  prepared.  A  solution  very  much 
used  in  preparing  heliographic  papers  has  a  specific 
gravity  of  45°  Baunie  (  =  1*45,  water  =1).  The 
ferric  chloride  liquor  of  the  British  Pharmacopoeia 
(liq.  ferri  perchloridi  fortis)  has  a  specific  gravity 
(1*42)  very  near  this,  and  contains  286  grains 
anhydrous  ferric  chloride  per  ounce,  or  653  grams 
per  litre. 

The  following  table,  enlarged  from  The  Photogram, 
1894,  page  139  (June),  gives  the  gravities  and 
strengths  of  ferric  chloride  solutions  : — 


Ferric 

Ferric 

Ferric 

Degrees 
Baume. 

Specific 
gravity. 

chloride, 
anhydrous. 
Grams  per 

chloride, 
anhydrous. 
Grams  per 

chloride, 

cryst.  * 

Grams  per 

100  grams. 

100  c.cs. 

100  c.cs. 

48 

1-501 

49 

74 

127 

45 

1-454 

47 

68 

118 

43 

1-426 

45 

64 

111 

40 

1-384 

41 

57 

98 

38 

1-359 

39 

53 

91 

36 

1-334 

37 

48 

85 

33 

1-298 

34 

44 

76 

30 

1-264 

31 

39 

68 

Ferric  ammonmm  citrate  is  purchased  in  thin, 
transparent  scales  of  deep  red  color  with  a  metallic- 
like  lustre.  It  is  soluble  in  half  its  weight  in  water 
to   a   clear   brown   solution.       If    the   crystals   are 


*  Calculated  on  basis  of  58  per  cent.  Fe2Cl6,  as  ascertained  l>y 
analysis. 


134  FERRIC   AND   HELIOGRAPHIC   PROCESSES 

opaque,  and  the  salt  forms  a  blue  solution  on  first 
dissolving  in  water,  decomposition  has  taken  place, 
and  such  salt  is  liable  to  yield  paper  which  will  not 
give  pure  whites. 

The  composition  of  the  brown  citrate  is  said  to  be 
4FeC6H507. 3(NHJ8.  C6H507. 3Fe(OH)3. 

Preparation. — When  circumstances  make  it  advis- 
able to  prepare  the  salt,  the  simplest  plan  is  to 
follow  the  instructions  of  the  British  Pharmacopoeia. 

Add  16  ounces  (320  c.cs.)  of  strong  ammonia  (sold 
as  #880)  to  40  ounces  (800  c.cs.)  of  water.  Add 
to  this,  little  by  little,  10  ounces  (200  c.cs.)  of 
ferric  sulphate  solution  (B.P.)  previously  diluted 
with  40  ounces  (800  c.cs.)  of  water.  Stir  well,  and 
set  aside  for  two  hours,  stirring  occasionally.  Filter 
on  a  calico  or  flannel  filter,  and  wash  the  residual 
ferric  hydrate  with  water  till  the  washings  give  no 
more  reaction  for  sulphate  (on  testing  with  a  few 
drops  of  barium  chloride  solution)  than  the  washing 
water  itself.  It  would,  of  course,  be  better  to 
wash  in  distilled  water,  but  ordinary  tap  water  will 
answer  almost  as  well.  Dissolve  4  ounces  (80 
grams)  of  citric  acid  in  its  own  weight  of  water, 
and  gently  warm  the  solution  on  a  water  bath. 
Add  the  ferric  hydrate  (well  drained)  and  stir 
together  till  nearly  the  whole  of  the  hydrate  has 
dissolved.  Let  the  solution  cool,  add  5|  ounces 
(110  c.cs.)  of  ammonia,  and  filter  through  flannel, 
adding  a  little  distilled  water,  if  filtration  proceeds 
too  slowly.  Evaporate  till  syrupy,  and  dry  on 
porcelain  or  glass  plates  at  a  temperature  not  above 
100°  Fahr. 


CHEMICALS  135 

The  green  ferric  ammonium  citrate  introduced 
by  Valenta  and  supplied  by  Merck,  is  stated  to 
have  the  composition  5FeCcH507. 2(NH4)3.  C6H507. 
NH4C6H507.2H20.* 

Ferric  oxalate  can  be  bought  crystallised,  but  is 
expensive.  It  occurs  in  small,  pale-bluish  green 
crystals  which  do  not  dissolve  readily  in  cold  water, 
but  very  readily  in  hot,  without  depositing  when 
the  solution  cools.  The  salt  and  its  solution  should 
be  kept  in  the  dark. 

Ferric  oxalate  is  easily  made  from  a  ferrous  or 
ferric  salt,  and  the  writer  gives  below  the  process 
and  quantities  of  chemicals  required  for  100  grams 
of  ferric  oxalate  in  20  per  cent,  solution.  The  reader 
who  wishes  to  use  English  weights  and  measures 
must  substitute  for  grams  some  English  unit  through- 
out— grains,  drachms,  or  ounces,  according  to  the 
quantity  he  requires. 

Iron  alum  or  ferric  chloride  solution  is  the 
simplest  raw  material  for  the  manufacture  of  ferric 
oxalate.  If  ferrous  sulphate  is  used  the  following 
preliminary  treatment  is  necessary. 

150  grams  (theory,  148)  of  protosulphate  of  iron 
are  dissolved  in  hot  water,  a  little  sulphuric  acid 
added,  and  then,  very  cautiously,  about  15  c.  cs.  of 
strong  nitric  acid  (sp.  gr.  1  "4).  The  liquid  must  be 
in  a  porcelain  basin.  Enamelled  iron  might,  with 
some  risk,  be  used.  The  first  addition  of  the  nitric 
acid  produces  a  dark  brown  color.  As  the  acid  is 
added  its  action  becomes  more  energetic,  and  at  the 

*  Photographische  Korrespondenz,  1897,  p.  77. 


136 


FERRIC    AND   HELIOGRAPHIC   PROCESSES 


end  of  the  process  (which  may  be  thus  recognised) 
the  liquid  bubbles  up,  giving  off  red  fumes  and 
becoming  clear  orange-red  in  color.  A  little  more 
nitric  acid  is  then  added,  and  the  liquid  allowed 
to  cool.  From  this  stage  the  solution  which  contains 
ferric  sulphate  and  nitrate  is  treated  exactly  as  the 
iron  alum  or  ferric  chloride  solution  to  be  now 
described. 

256  grams  iron  ammonium  alum,  or  132  c.cs. 
ferric  chloride  solution  (B.P.,  sp.  gr.  1*42),  are 
diluted  with  water  to  about  1000 
c.cs.  and  poured  into  100  c.cs. 
strong  ammonia  diluted  to  a  like 
amount.  The  alkaline  liquid 
may  be  contained  in  a  clean  tin 
vessel.  The  precipitated  ferric 
hydrate  is  allowed  to  settle,  the 
clear  liquid  syphoned  off,  and 
some  boiling  water  stirred  up 
with  the  residual  precipitate. 
The  whole  is  then  poured  on 
to  a  flannel  or  calico  filter  (fig. 
20)  and  washed  for  several  hours 
in  a  current  of  cold  water, 
being  occasionally  well  stirred 
up  on  the  filter  with  a  piece 
of  glass  rod,  rounded  at  the 
end,  or  a  silver  spoon.  As  much  as  possible  of  the 
liquid  is  squeezed  out  of  the  flannel,  and  the 
precipitate  scraped  out  with  a  silver  spoon  into  a 
porcelain  basin. 

All  the  foregoing  operations  may  be  performed  in 


Fig.  20.— Filter  for 
washing  Ferric 
Hydrate. 


CHEMICALS  137 

broad  daylight.     The  remaining  part  of  the  process 
must  be  conducted  in  a  dark  room. 

100*5  grams  of  finely  powdered,  pure  oxalic  acid 
are  sprinkled  over  the  precipitate,  mixed  up  with  it, 
the  dish  covered  over  and  left  to  itself,  save  for 
occasional  stirring,  for  a  day  or  two.  The  process 
of  solution  may  be  hastened  by  heating  to  not  above 
85°  Fahr.  :  for  this  a  small  oil  stove  placed  some 
distance  below  the  dish  answers  well.  Test  the 
temperature  with  a  thermometer  ;  if  it  goes  much 
above  85°  Fahr. ,  the  salt  is  partly  reduced  to 
ferrous  oxalate.  The  solution  gradually  turns  from 
pure  green,  through  yellowish-green,  to  greenish- 
brown.  This  strong  solution  must  be  diluted  with 
distilled  water  till  it  measures  500  c.cs.  10  c.cs. 
then  contain  2  grams  :  it  will  keep  indefinitely  in  a 
cool  and  dark  place. 

Potassium  ferrocyanide  (yellow  prussiate  of  potash) 
occurs  in  large  lemon-yellow  crystals,  sometimes 
turbid  or  translucent  (not  a  sign  of  impurity).  The 
salt  keeps  well,  exposed  to  light  and  air,  has  a 
neutral  reaction,  and  is  not  poisonous.  The 
saturated  solution  (at  60°  Fahr.)  contains  259  grams 
per  litre  and  has  a  specific  gravity  of  1  "14 

Potassium  ferricyanide  (red  prussiate  of  potash) 
forms  fine,  large,  blood-red  crystals  which,  when  the 
salt  is  pure  and  fresh,  are  transparent.  The 
powdered  salt  is  orange-red.  Exposed  to  light,  both 
in  the  solid  state  and  in  solution,  it  is  decomposed 
with  formation  of  ferrocyanide  and  of  a  blue  pre- 
cipitate. It  is  therefore  very  important  to  store  the 
solution  (well  stoppered)  in  the  dark  and  to  rinse 


138  FERRIC    AND   HELIOGRAPHIC   PROCESSES 

crystals,  which  are  not  clear  ruby  red,  with  a  little 
water — drying  them  between  blotting-paper — before 
weighing  them.  The  concentrated  solution  is 
brownish  -  yellow  ;  the  weak,  lemon  -  yellow.  100 
parts  of  water  dissolve  nearly  40  parts  of  the  salt  at 
ordinary  temperature. 

Uranium  acetate,  nitrate  and  chloride  resemble 
one  another  in  their  general  properties.  They  are 
all  very  soluble  in  water, — 50  parts  in  100  parts  of 
water. 

Gallic  acid  ought  to  be  nearly  white  needles,  but 
is  often  of  a  brownish  tinge.  One  part  dissolves  in 
130  parts  of  cold  water,  3  parts  of  boiling  water,  12 
of  glycerine,  and  5  of  alcohol. 

Tannic  Acid. — Light  brownish  powder  of  thin 
glittering  scales.  It  is  very  soluble  in  water, 
alcohol,  or  glycerine.  One  part  of  either  of  these 
solvents  dissolves  one  part  of  the  acid. 

Gum  arabic  is  nearly  colorless,  but  often  has  a 
yellowish  tint  :  it  should  be  nearly  inodorous.  It 
is  insoluble  in  alcohol  and  very  soluble  in  water, 
forming  a  translucent  viscid  solution,  which  is 
thickened  or  rendered  turbid  by  ferric  salts.  The 
price  of  gum  arabic  varies  from  two  shillings  to  four 
shillings  and  sixpence  per,,  pound,  according  to  its 
purity.  One  of  the  best  brands  is  '  White  Senaar, ' 
another  '  Senegal. ' 


CHEMISTRY  139 


CHAPTEE    XXII 

Chemistry 

Ferrous  and  Ferric  Salts. — There  are  two  series  of 
salts  of  iron — the  ferrous  and  the  ferric'.  They  differ 
in  the  proportion  of  oxygen  (or  other  negative 
element,  such  as  chlorine)  which  they  contain.  Fer- 
rous chloride,  FeCl2,  may  be  taken  as  typical  of  the 
ferrous  series,  and  ferric  chloride,  Fe2Cl6,  of  the  ferric 
series.  It  is  quite  easy,  by  chemical  means,  to 
convert  any  member  of  one  series  into  the  corre- 
sponding member  of  the  other.  Thus,  reducing 
agents,  substances  like  sulphurous  acid,  which 
readily  combine  with  (and  remove  from  any  com- 
pound) oxygen,  chlorine,  or  similar  electro-negative 
elements,  convert  ferric  salts  into  ferrous  ;  whilst 
oxidising  agents,  substances  like  nitric  acid  or 
potassium  permanganate,  which  readily  supply 
oxygen,  chlorine,  or  similar  elements  to  any  com- 
pound, convert  ferrous  salts  into  ferric  salts. 
.  Chemical  and  Photo-chemical  Reduction  of  Ferric 
Salts. — The  above  chemical  reactions  go  on  irrespec- 
tive of  the  action  of  light,  though  heat  is  sometimes 
necessary  to  start  or  complete  them.  There  are, 
however,  certain  reducing  agents  which  convert 
ferric  into  ferrous  salts  only  under  the  influence  of 


140  FERRIC  AND   HELIOGRAPHIC   PROCESSES 

light.  For  instance,  a  solution  of  ferric  chloride  in 
ether  remains  quite  unaltered  in  the  dark,  but  on 
exposure  to  sunshine  soon  loses  its  yellow  color  and 
becomes  reduced  to  ferrous  chloride,  the  change  being 
accompanied  by  the  decomposition  of  a  portion  of 
the  ether. 

Paper,  too,  saturated  with  a  solution  of  ferric  chlo- 
ride and  dried,  is  similarly  capable  of  effecting  the 
reduction  of  the  ferric  salt.  These  changes — not 
merely  chemical,  but  photo-chemical — are  examples 
of  many  which  take  place  not  in  the  case  of  salts  of 
iron  only,  but  of  compounds  of  uranium,  cobalt, 
manganese,  chromium,  and  other  metals. 

There  is  one  distinguishing  feature  common  to  the 
bodies  which  undergo  photo-chemical  decomposition 
in  this  way — or  at  any  rate  to  those  of  which  any 
practical  use  can  be  made.  They  are  all  compounds 
of  elements  which,  like  iron,  are  capable  of  existing 
in  two  states  of  oxidation.  It  is  generally  only  the 
more  highly  oxidised  compounds  which  are  sensitive 
to  light,  the  decomposition  resulting  in  the  formation 
of  a  salt  of  a  lower  degree  of  oxidation,  and  in  order 
that  photo-chemical  action  shall  take  place,  it  is 
necessary  that  the  metallic  salt  shall  be  associated 
with  a  mild  reducing  agent  such  that  when  exposed 
to  light,  the  reduction  of  the  ferric  (or  other)  salt 
and  the  oxidation  of  the  reducer  shall  go  on  together. 

If  the  reducer  is  too  powerful,  decomposition  takes 
place  without  the  aid  of  light  at  all  (ferric  chloride 
and  sulphurous  acid)  :  if  no  compound  is  present 
which  can  take  up  the  oxygen  or  other  element  ^rom 
the  compound  exposed  to  light,  no  photo-decomposi- 


CHEMISTRY  141 

tion  takes  place  (ferric  chloride  in  aqueous  solution) : 
whilst  the  case  of  ferric  chloride  in  ethereal  solution 
is  an  example  of  the  principle  just  cited,  of  exposing 
a  substance  in  the  presence  of  a  second,  capable  of 
promoting  its  decomposition  in  the  light.* 

This  reducing  matter  need  not  necessarily  be  a 
separate  compound  :  it  may  be  combined  with  the 
ferric  salt,  as  when  organic  salts  of  iron  (oxalate  or 
citrate)  are  made  use  of. 

The  chief  compounds  of  which  practical  use  has 
been  made  are  the  ferric  and  the  alkaline  bichromates, 
and  the  processes  which  have  been  developed  depend 
on  the  differences  in  the  behaviour  of  various  reagents 
towards  these  salts  and  their  lower  compounds.  For 
example,  ferrous  salts  reduce  the  noble  metal  from 
compounds  of  platinum  or  silver,  whilst  no  such  action 
is  exerted  by  the  ferric  salts — a  difference  which  is 
the  basis  of  the  platinotype  and  Kallitype  processes. 

Action  of  Light.  Ferric  Salts.  — The  ferric  salts  of 
mineral  acids  (such  as  sulphuric,  hydrochloric)  are 
reduced  to  the  corresponding  ferrous  salts  when  ex- 
posed to  light  with  various  organic  bodies,  such  as 
oxalic  acid,  citric  acid,  tartaric  acid,  gelatine,  gum, 
etc. ,  whilst  a  similar  change  takes  place  in  the  case 
of  organic  salts  of  iron  like  the  oxalate,  tartrate,  and 
citrate.  Very  often  the  use  of  a  double  salt  of  iron 
and  ammonia  gives  better  results,  and  the  reason 
ascribed  is  that  the  ferric  salt  possesses  the  property 
of  dissolving  the  newly  formed  ferrous  salt  to  such 
an  extent  as  to  weaken  the  vigour  of  the  image.     The 

*  See    Chemistry  of  Photography,    by   Raphael   Meldola,   Mae- 
raillan,  1891,  pp.  12-20  and  71-82. 


142  FERRIC   AND   HELIOGRAPHIC   PROCESSES 

introduction  of  ammonia  into  the  compound  counter- 
acts this  solvent  action,  and  hence  ferric  ammonium 
citrate,  ferric  ammonium  oxalate,  etc. ,  are  compounds 
which  are  very  frequently  used  in  preference  to  the 
simple  iron  salts. 

Uranium  Salts. — The  metal  uranium  forms  two 
series  of  salts — the  uranic  (yellow  solutions)  and 
uranous  (green  solutions).  The  salts  most  used  are 
uranic  nitrate,  chloride,  and  acetate,  though  the 
organic  salts  of  uranium  offer  a  promising  field  for 
experiments.  On  exposure  to  light,  uranous  oxide, 
U02,  and  the  uranous  salt  of  the  acid  are  generally 
produced.  * 

Chromium  Compounds. — Exposed  to  light  in  con- 
tact with  organic  substances  such  as  gum,  gelatine, 
etc. ,  alkaline  bichromates  (K2Cr207)  become  reduced 
to  chromium  salts,  whilst  the  associated  organic 
matter  has  several  of  its  physical  properties  modified. 
Both  of  these  changes  are  utilised  in  one  process  or 
another  for  the  production  of  an  image. 

Thus,  the  unaltered  chromate  reacts  with  silver 
nitrate,  giving  a  red  precipitate  of  silver  chromate, 
whilst  the  reduced  chromium  salt  does  not ;  but  the 
most  important  processes  are  those  dependent  on  the 
alteration  of  the  gum  or  gelatine.  The  principal 
changes  are  in  (1)  solubility,  (2)  hygroscopic  pro- 
perties, (3)  power  of  imbibition  (or  ability  to  absorb 
water). 

(1)  Gelatine  or  gum,  mixed  with  bichromate,  and 
exposed  to  light,  becomes  insoluble  in  hot  water,  a 

*  Vide  Burnett's  "  Researches,"  British  Journal  of  Photography, 
1857  and  following  years. 


CHEMISTRY  143 

change  which  is  the  basis  of  the  well-known  carbon 
and  similar  processes. 

(2)  Bichromatecl  gum  or  dextrine  is  tacky  before 
exposure  to  light,  but  after  exposure  is  found  to  have 
lost  this  property,  so  that  a  fine  powder  does  not 
adhere  to  the  exposed  portions  {anthrakotype  and 
other  '  powder  '  processes). 

(3)  Bichromated  gelatine,  exposed  to  light,  loses 
its  power  of  swelling  by  absorption  of  water,  and  if  a 
gelatine  surface,  some  parts  of  which  have  been  ex- 
posed and  others  not,  be  immersed  in  cold  water,  and 
a  roller,  charged  with  greasy  ink,  then  passed  over 
it,  the  ink  is  repelled  from  the  unexposed  portions, 
but  adheres  to  the  unswollen  portions  (basis  of 
papyrotype,  page  113,  heliotype,  and  other  processes). 

As  explained  above,  all  these  printing  processes 
with  metallic  salts — to  use  a  long  phrase  for  what 
the  Germans  call  Lichtpausverfahren — depend  on  the 
difference  in  action  of  certain  reagents  on  the  salts 
and  on  their  products  when  exposed  to  light. 

The  principal  reagents  are  potassium  ferrocyanide, 
potassium  ferricyanide,  gallic  and  tannic  acids,  and 
silver  nitrate.  By  referring  to  the  reactions  given 
below,  the  student  will  be  able  to  understand  the 
theory  of  the  processes  described  in  these  papers. 

Potassium  Ferrocyanide.  Ferric  Salts.  — Deep  blue 
precipitate  of  Prussian  blue. 

3K4Fe(Ctf  )6  +  Fe2Cl6  =  3Fe(CN)2.2Fe2(CN)6  +  12KC1. 

Ferrous  Salts. — Bluish   white   precipitate,    which 
rapidly  becomes  blue  on  exposure  to  the  air. 
K4Fe(CN)6  +  FeS04  =  K2Fe.Fe(Ctf)e  +  K2S04. 


144  FERRIC   AND   HELIOGRAPHIC   PROCESSES 

Uranic  Salts.  — Ked-brown  precipitate. 

Uranous  Salts.  — Ked-brown  precipitate. 

Potass  Ferricyanide.  Ferric  Salts.  —  No  pre- 
cipitate :  merely  a  brown  coloration. 

Ferrous  Salts. — Deep  blue  precipitate  of  Turnbull's 
blue,  Fe3.Fe2(CN)12. 

Uranic  Salts. — No  precipitate. 

Uranous  Salts.  — Ked-brown  precipitate  of  uranous 
ferricyanide. 

Tannic  Acid.  Ferric  Salts. — Intense  bluish-black 
precipitate. 

Ferrous  Salts. — In  strong  solutions  a  white  gela- 
tinous precipitate  :  none  in  weak  solutions. 

Uranic  Salts.  — ? 

Uranous  Salts. — Ked-brown  precipitate. 

Silver  Nitrate.     Ferric  Salts. — No  reaction. 

Ferrous  Salts.  — Precipitate  of  metallic  silver. 

Uranic  Salts. — No  reaction. 

Uranous  Salts.  — Precipitate  of  metallic  silver. 

Alkaline  Ohromate. — Ked  precipitate  of  silver 
chromate. 

Chemistry  of  Prussian  Blue. — It  would  be  out  of 
the  scope  of  this  work  to  discuss  the  chemical  con- 
stitution of  the  several  varieties  of  Prussian  blue. 
The  student  should  refer  to  an  article  by  W. 
Dittmar,*  where  the  chemistry  of  the  question  is 
discussed.  But  some  of  the  chemical  and  physical 
qualities  of  these  blues  are  of  practical  importance 
from  the  present  point  of  view. 

On  exposure  to  bright  light  Prussian  blue  fades  a 

*  Thorpe's  Dictionary  of  Applied  Chemistry,  vol.  i.  p.  640. 


CHEMISTKY  145 

little,  and  regains  its  original  intensity  of  color  in 
the  dark. 

Caustic  and  carbonated  alkalies  (caustic  soda  and 
washing  soda)  decompose  it,  separating  a  hydrated 
oxide  of  iron  and  forming  a  soluble  ferrocyanide — 

Fes.Fe2(CN)12  +  8KOH=  2K4Fe(CN)6  +  Fe804.4H20. 

The  same  result  is  produced,  though  much  more 
slowly,  by  solutions  of  carbonate  of  lime  and  of 
magnesia ;  and  as  these  salts  are  the  almost  in- 
variable constituents  of  ordinary  drinking  waters, 
the  point  is  of  practical  importance.  If  washed  too 
long,  the  blue  image  is  very  considerably  weakened. 

Silver  nitrate  and  mercuric  sulphate  act  very 
powerfully  on  Prussian  blue,  destroying  the  blue 
color  :  the  latter  salt  forms  cyanide  of  mercury  and 
sulphate  of  iron. 

Oxalate  of  potash  immediately  decolorises  and 
dissolves  Prussian  blue  :  so  does  cuprous  chloride 
(subchloride  of  copper)  dissolved  in  weak  hydro- 
chloric acid. 


10 


BIBLIOGKAPHY 


Berg,   Die   Herstellung   von   LichtdrucJcbildern,    schwarz 

und  farbig,  ohne  Presse,  etc.     Cleve,  1892. 
Blue   Print    Making    (reprinted   from    Carpentry   and 

Building).       New     York  :    David    Williams     Co., 

1900. 
Blue   Print,    No.    10    of    The    Photo- Miniature.     New 

York :    Tennant  &   Ward ;    London :    Dawbarn   & 

Ward,  Ltd.,  1900. 
Bry,    Traite   de    V  Aidographie.      Lacroix,    edit.,    Paris, 

1861. 
Cheysson,      Manuel     des     Procedes     de     Reproduction 

cVEcriture  et  de  Dessin  a,  employer  dans  le  Service 

des  Ponts  et  Chaussees.     Paris,  1880. 
Colson,  Procedes  de   Reproduction   des   Dessins   par   la 

lumiere.     Gauthier-Villars,  edit.,  Paris,  1888. 
Duchochois,      Photographic      Reproduction     Processes. 

London  :  Hampton,  Judd  &  Co.,  1892. 
Eder,   Das    Lichtpausverfahren,    die    Platinottjpie    und 

verschiedene  Copirverfahren  ohne  Silbersalz.    Knapp, 

Halle,  A.S.,  1899. 
Ettinghausen     und     Pokorny,     Der     wissenschdftliche 

Anwendung    des    Naturselbstdruckes   zur   graphische 

Darstellung  von  Pjianzen.  Wien,  1856. 
Fisch,  La  Photocopie.  Michelet,  Paris,  1886. 
Fisch,  Nouveaux  Procedes  de  Reproductions  industrielles. 

Michelet,  Paris,  1887. 
Gioppi,  La  Fotografia  Industrials     1898. 
Haugk,  Lichtpausverfahren.     Grieben,  Berlin,  1875. 

146 


BIBLIOGRAPHY  1 47 

Kallitype,     No.     47     of     The    Photo- Miniature.      New 

York  :    Tennant    &    Ward  •    London  :    Dawbarn  & 

Ward,  Ltd.,  1903. 
Lallemand,    Nouveaux     Procedes    d' Impressions    auto- 

graphique.     Leiber,  Paris,   1868. 
Liesegang,      Die      modernen     Lichtpausverfahren     zur 

Herstellung   exacter   Copien  nach   Zeichnungen,  etc., 

mit   Hilfe   lichtempfindlicher    Papiere.      Liesegang, 

Dusseldorf,  1884. 
Lietze,  Modem  Heliograpliic    Processes :    Instructions  in 

the  Art   of  reproducing  Drawings  and  Engravings, 

etc.,  by  the  Action  of  Light.     London,  1889. 
Maihak,  Die    Vervielfdltigunq   von  Zeichnungen,  insbes- 

ondere     von     technischen    Zeichnungen,      Springer, 

Berlin,   1888. 
Masselin,  Traite  pratique  de  Photographie  appliquee  aux 

Dessins  Industriels.     Gauthier-Villars,  Paris,  1890. 
Pizzighelli,    Anthrahotypie    und    Cyanotypie.      Knapp, 

Halle,  A.S.,  1881. 
Poitevin,    Traite    de    V Impression   photographique   sans 

sels  d'1  Argent.     Gauthier-Villars,  Paris,  1883. 
Sohuberthe,  Lichtpausverfahren  oder  die  Kunst  genaue 

Copien  mit  Hilfe   des  Lichtes  unter   Beniitzung  von 

Silber,      Eisen,      und      Ohromsalzen      herzustellen. 

Hartleben,  Wien,   1893. 
Talbot,  Der  Lichtpaus-Process.     Talbot,  Berlin,  1873. 
Thwaite,  Proc.  Inst.  Civ.  Eng.,  1885-86.     Pt.  IV. 
Volkmer,  Mittheilungen   iiber   einige   neuere   und   inter- 

essante  Arbeiten  auf  den  Gebiete  der  Photographie 

und    der    Reproductions-Technik    der    graphischen 

Kunst.     Wien,   1886. 
Waterhouse,    Practical    Notes   on   the    Preparation   of 

Drawings  for  Photographic  Reproductions.     London, 

1890. 


INDEX. 


Abney's  papyrographic  process, 

113. 
Aniline  process  (Willis's),  105. 
Anthrakotype,  111. 

Baths,  washing  and  developing, 

85. 
Blue  paper,  11,  59,  90. 
Blue  prints,  over-printed,  92. 

,,  under-printed,  93. 

"  Blue  solving,5'  115. 
Bolle's  toning  process,  19. 
Brewerton,  W.  E.,  color  prints, 

29. 
Brown  line  (sepia)  paper,  40,  73, 

102. 

Carter's    process    (prints    in 

dyes),  54. 
Catechu  toning,  17. 
Chromate  pigment  processes,  107. 
Coating,  13,  120. 
Coating  machinery,  62. 
Color  photography,  Ferro-prus- 

siate  in,  29. 
Cyanofer,  57. 

Drawing  papers  (sizes),  116 
Drying  copies,  86. 

,,      paper,  62,  122. 
Dyes,  prints  in,  54. 

Electric  light  for  printing,  79. 


Engineers,  processes  for,  56. 
Exposure,  ferro-gallic  paper,  99. 

,,         ferro-prussiate,  90. 

,,  Pellet  paper,  94. 

Fabrics,  prints  on,  53. 
Ferric  oxalate,  making,  136. 
Ferrogallic,  70,  99. 
Ferro-prussiate,  11,|59,  90. 
Filtering,  118. 
Floating  paper,  121. 

Hargreaves'  process  (prints  in 

dyes),  55. 
Hydrometers,  117. 

Intensifying  blue  prints,  22. 
Iron  pigment  process,  106. 
Itterheim's  process,  108. 

Kallitype,  32. 
Kallitypes,  reducing,  39. 

Linaura  fabric,  129. 
Long  tracings,  printing,  83. 

Machines  for  coating,  62. 
Mafeking,  blue  prints  at,  23. 
MonselFs  salt,  21. 
Mounting  prints,  116. 

"Negative"  processes  for  en- 
gineers, 56. 


u: 


INDEX. 


149 


Newspaper  work,  blue  prints,  28. 
,,  ,,    Kallitype,  43. 

Obernetter  process,  45. 
Oiling  drawings,  115. 

Papers,  raw,  126. 

Papyrographic  process,  113. 

Pellet  paper,  57,  68,  94. 

Pigment  processes,  106. 

Poitevin's  process,  106. 

"Positive  ferrotype,"  57. 

"Positive"    processes    for    en- 
gineers, 56. 

Postcards,      blue     prints      as, 
24. 

Printing  by  electric  light,  79. 
,,        frames,  77. 
,,        house,  88. 

Reducing  blue  prints,  22. 
Register,  negative,  23. 
Removing  lines  from  blue  prints, 

115. 
Reynolds'  formulae,  15. 
Roy's  toning  process,  17. 

Sepia  paper,  40,  73,  102. 


Silver  processes,  113. 

Sizes  of  drawing  papers,  116. 

Sizing  paper,  129. 

Spaulding's    printing  machine, 

83. 
Stains,     removing     from     blue 

prints,  115. 
Storage  of  papers,  125. 

Toning  blue  prints,  17. 
Tracings,  making,  75. 
Transparencies,  blue-print,  24. 
Transparent,  making  drawings, 

115. 
Tri-color    work,    ferro-prussiate 

in,  29. 

Uranium  salts  in  ferro-prussiate, 

15. 
Uranotype  process,  49. 

Valenta's  formula,  14. 
Varnishing  prints,  116. 
Vertical  washing  trough,  87. 

Water  for  washing  blue  prints, 

89. 
Weights  and  measures,  117. 


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